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NetLogo 1.1 User Manual

1. X Rotatable and scalable vector turtle shapes Redesigned user interface X Text labels tor turtles and patches X Je mme X BehavioSpace a tool used to collect data from multiple runs of a model X HubNet participatory simulations using networked handheld devices X ConvertsStarLogoT models into NetLogomodels Syntax highlighting code editor What is NetLogo What s New Feedback from users is very valuable to us in designing and improving NetLogo We d like to hear from you Please send comments suggestions and questions to feedback ccl northwestern edu and bug reports to bugs Q2ccl northwestern edu Version 1 1 Rev D August 2002 e content fixed links in PDF version of User Manual that took you to the wrong page the Known Issues section of the User Manual now lists a few more known bugs improved models Rabbits Grass Weeds better default slider settings Painted Desert Challenge better default slider settings CA 1D suite faster clearer code adjusted the interfaces of many models so that texts don t get cut off even on Java VMs with a large default font size e engine fixes fixed slight periodic bias in random number generator when generating small integers several fixes to in radius it now wraps around the edges and handles radii larger than screen edge x y properly and no longer leaves out some turtles near the edge of the circle fixed case where the c
2. A O bserver Turtles Patches or use Tab key e Choose Turtles from the popup menu or use the tab key e Type set color pink and press return e Choose Patches from the popup menu or use the tab key eType set pcolor white and press return What does the Graphics Window look like now What was omitted in these two commands but not in the observer command from the earlier exercise The observer oversees the world and therefore can give a command to the patches or turtles using ask Like in the case above the observer has to ask the patches to set their color to yellow But when a command is directly given to a group of agents like in the second example you only have to give the command itself Tutorial 2 Commands 28 NetLogo 1 1 User Manual e Press setup What happened Why did the Graphic Window revert back to the old version with the black background and white road This is because the effects of commands given in the Command Center are temporary Upon pressing the setup button the model will reconfigure itself back to the settings outlined in the Procedures tab The purpose of the Command Center is not to permanently change the model It is a tool to customize current models and allows for you to manipulate the NetLogo world to further answer those What if questions that pop up as you are investigating the models The Procedures tab is explained in the next tutorial and in the Programm
3. n newline carriage return e t tab e double quote e backslash Turtle shapes In StarLogoT turtle shapes were bitmaps They all had a single fixed size and could only rotate in 45 degree increments In NetLogo turtle shapes are vector shapes They are built up from basic geometric shapes squares circles and lines rather than a grid of pixels Vector shapes are fully scalable and rotatable A turtle s shape is stored in its shape variable and can be set using the set command Programming Guide 68 NetLogo 1 1 User Manual New turtles have a shape of default The set default shape primitive is useful for changing the default turtle shape to a different shape or having a different default turtle shape for each breed of turtle Use the Shapes Editor to create your own turtle shapes For more information see the Shapes Editor section of this manual Code Examples Breeds and Shapes Example Shape Animation Example Programming Guide 69 HubNet Guide HubNet is a technology that lets you use NetLogo to run participatory simulations in the classroom In a participatory simulation a whole class takes part in enacting the behavior of a system as each student controls a part of the system by using an individual Tl 83 calculator For example in the Gridlock simulation each student controls a traffic light in a simulated city with their calculator The class as a whole tries to make traffic flow efficient
4. a 104 e HO EE 105 PESE aE eee ES or eR OPP Re Be EER OUP ECan I EI oN Pe ere or 105 Uc AR 105 fe Lee 106 distanc S ro a Lore re A AA 106 AEE 4 T ET A E 106 digi TA Gu bed enia inves boe bb blo ON rem alas lad EM Latin acide bain rui pK 106 A A 106 Sir 107 A EU 107 UNE I M os 107 e rm Pm 108 GIRONE RTT iia EEN E AEA E E A TERA EE ER 108 BUDE Ic d E et Eu S M ELM LS MU e oa 108 Pates 108 export output export plot evport wotrld 109 ELETRE TI eect creation EE 109 E as aida uou be eM an DIM MN ME MM AERE 110 bounds DEM danse otal E E n DE LUE PR D MU SE RI M EET 110 ll e D cuu Ln ae en hoe M UM E E M Mi M ET 110 Ehe 110 Let Aes o tec ae tee LUE seth MC MM ek E MEE 110 e M 111 PT cC cC oP Ae Nene EE SORE SMM rm Re ERY eRe RA 111 A TT RU PT 111 Eoo o seu I I ME 111 ELE 111 RI Aa A E EEE E EAAS A AAEL E 111 HSO MITT Dep 112 DISPENSE usce alc ee e a E Mec tta uc MM erc aL 112 HII NEU A AE 112 lk eR TR UNUM r o T 113 AU Ee SELE SL osuere rrt aa teta ec ta tico E 113 a TERT COT DRE 113 um SR UC 113 Fiet message SOU E E 113 hubnet message lag ROTE t 114 W eiiim UN cr iios c LL DETECTOR a ia 114 ul Ee 114 hubnet set client interface nana nano nanananonnnnnanos 114 O cm imo TTE 114 Eorum M ceer eer 115 EE T UU PEE 115 licis e UT eee 115 luos A CTS rer 115 Ts eal 8 UIE oe cen mc ee 116 NetLogo 1 1 User Manual Table of Contents Primitives Dictionary A T NR RU
5. Compile Halt lete Edit Button Slider Sw Now switch to the Procedures Tab and create the setup procedure like this Compile Find Find Again to setup ca crt 100 ask turtles fd random screen edge x end One line at a time to setup begins defining a procedure named setup ca is short for clear all you can also spell it out if you want This command will blank out the screen initialize any variables you might have to 0 and kill all turtles Basically it wipes the slate clean for a new run of the project crt 100 will then create 100 turtles Each of these turtles will begin on the center patch at location 0 0 That s why you only see what looks like one turtle on the screen they re all on top of each other lots of turtles can share the same patch Only the last turtle to arrive on the patch is visible Each of these newly created turtles has its own color evenly distributed through the range of NetLogo colors and its own heading evenly distributed around the circle ask turtles tells each turtle to execute independently the instructions inside the brackets Note that crt is not in brackets If the agent is not specified the observer executes it fd random screen edge x is really a pair of commands Each turtle will first evaluate the expression random screen edge x which will return a random value between 0 and screen edge x the dimension from the center to the edge of the screen along the x axis may
6. In Tutorial 3 Procedures you can learn how to alter and extend existing models and build your own models Tutorial 41 Models 25 Tutorial 2 Commands In Tutorial 1 you had the opportunity to view some of the NetLogo models and you have successfully navigated your way through the menu bar the toolbars opening and running models and gathering information from a model In this section the focus will start to shift from observing models to manipulating models You will start to see the inner workings of the models and be able to change how they look Sample Model Traffic Basic e Go to the Models Library File menu Open up Traffic Basic found in the Social Science section e Run the model for a couple minutes to get a feel for it e Consult the Information tab for any questions you may have about this model In this model you will notice one red car in a stream of blue cars The stream of cars are all moving in the same direction Every so often they pile up and stop moving This is modeling how traffic jams can form without any cause such as an accident a broken bridge or an overturned truck No centralized cause is needed for a traffic jam to form You may alter the settings and observe a few runs to get a full understanding of the model As you are using the Traffic Basic model have you noticed any additions you would like to make to the model Looking at the Traffic Basic model you may notice the
7. LAX NL JAVA OPTION JAVA HEAP SIZE MAX allow the heap to get huge lax nl java option java heap size max 536870912 We have tested NetLogo with models that use hundreds of megabytes of RAM and they work fine We haven t tested models that use gigabytes of RAM though It should work but eventually perhaps you might hit some limits that are inherent in the underlying Java VM virtual machine and or operating system either built in limits or just bugs related to extremely high memory use When will NetLogo be a native app on Mac OS X We can t promise but our plan is for NetLogo 1 2 to run natively under OS X The release of 1 2 is planned for Fall 2002 You can actually run NetLogo 1 1 natively under OS X though this is not officially supported If you want to try it just double click the nLogo jar file in the NetLogo folder Note you may encounter bugs and your model may run slowly Note that it s only graphics that are slow particularly turtle shapes The no display command will make your model run at normal speed although you won t be able to see what s going on Can import a graphic into NetLogo At present no We plan to add this capability in a future version FAQ Frequently Asked Questions 90 NetLogo 1 1 User Manual My model runs slowly How can speed it up Here s some ways to make it run faster without changing the code e If your model is using all available RAM on your computer then instal
8. Right below the row of tabs is a toolbar containing a row of buttons The buttons available vary from tab to tab Interface Tab The Interface Tab is where you watch your model run It also has tools you can use to inspect and alter what s going on inside the model When you first open NetLogo the Interface tab is empty except for the Graphics Window where the turtles and patches appear and the Command Center which allows you to issue NetLogo commands Interface Toolbar The toolbar contains all of the interface elements that are needed to display information in the Interface tab 9 9 0 7 xw oka Compile Halt Button Slider Switch Monitor Plot Text It is divided into sections with the left side containing two general controls that can be accessed from any tab compile and halt Compile is a command that filters through the procedure looking for any syntax errors Halt is an emergency stopping mechanism used only when the model is stuck The other buttons in the toolbar are described below Working With Interface Elements Selecting To select an interface element drag a rectangle around it with your mouse A gray border will appear around the element to indicate that it is selected Selecting Multiple Items You can select multiple interface elements at the same time by including them in the rectangle you drag If multiple elements are selected one of them is the key item which means that if you use the Edit or Delete bu
9. SA o EE 137 CITRUS 137 EE 138 e die NETT TD D UL ST LUTTE 138 BE ons c A LI I MI AM UE MM 138 NetLogo 1 1 User Manual Table of Contents Primitives Dictionary SE PMI RA 138 primes aaa 138 Stans dubii uc DIEM NUM MN LM MU reece EIE I 139 lem T mmm 139 SUI an all 139 O 139 jnre 140 O 140 dac E 140 A EA EE E E AEE E EN ORAA E E AAE EAEE ATT A 140 EEE B unctus E ALIUM UBI A II re uL 140 towards towards RUI ainia 141 TWA SITO Wero No Wi E 141 QUIT T T 141 e T E EU E 141 FU ies st SEIS Doo airada EE 142 turtles here BREED here 142 Turlles ow E Ee 142 RN once Mu ELM aM NM a Rd quU OM ns uM M BD ILE 143 AA aul pace bonnie ba UERSUM DM E EET 143 Sc ri T 143 DIU is e II ca hela TRU BEC NETT 144 Wie RESTE TO TOT EE TD 144 LEE DUE seii A a Pe DRE DE bbw iL lade dr D RUNE FEET REDE DAR aida 144 BE E m TER 144 TC me 144 EA EV OITA oi Soa IEEE TEE 145 MES AN OM is see TM 145 OE agi ee eens catenin ei EL ML lei aie MS eee 145 a Te o A E IA os 145 CT BEEE E kee E P I I e E TM 145 O e A T 146 EE 146 MAA sca as iaa iia 146 EE 147 Veil ne dI QST rs 147 er 147 DO Ee 147 viii What is NetLogo NetLogo is a programmable modeling environment for simulating natural and social phenomena It is particularly well suited for modeling complex systems developing over time Modelers can gi
10. You can make a global variable by adding a switch or a slider to your model or by using the globals keyword at the beginning of your code like this globals clock You can also define new turtle and patch variables using the turt1es own and patches own keywords like this turtles own energy speed patches own friction These variables can then be used freely in your model Use the set command to set them If you don t set them they ll start out storing a value of zero Global variables can by read and set at any time by any agent As well a turtle can read and set patch variables of the patch it is standing on For example this code ask turtles set pcolor red causes every turtle to make the patch it is standing on red In other situations where you want an agent to read or set a different agent s variable you put of after the variable name and then specify which agent you mean Examples set color of turtle 5 red turtle with ID number 5 turns red Programming Guide 59 NetLogo 1 1 User Manual set pcolor of patch 2 3 green 77 patch with pxcor of 2 and pycor of 3 turns green ask turtles set pcolor of patch at 1 0 blue every turtle turns the patch to its east blue ask patches with any turtles here set color of random one of turtles here yellow On every patch a random turtle turns yellow Colors NetLogo represents colors as numbers in the range 0 to 140 with the exception of
11. a procedure where an agentset was stored in a local variable e interface fixes now when you open a widget editor the contents of the default field are selected and when you use the Tab key the contents of the next field become selected fixed bug where occasionally button presses were ignored now if you try to open a file that is not a valid NetLogo model you get a warning instead of it just failing silently fixed bug where monitors set to a very high number of decimal places such as 20 sometimes had a slight rounding error numerous fixes to sliders including 0 fixed rounding errors where sliders could return slightly incorrect values that differed from the correct values in the 15th decimal place or so 0 fixed handling of various unusual values or combinations of values for minimum maximum and increment 0 appearance when zoomed is improved e BehaviorSpace improvements added an Export Plot button and an Export Behavior Data button improved behavior of plots with respect to using consistent axes across model runs assorted small usability improvements e HubNet improvements all six HubNet activities revised and improved no more TI 83 button login is initiated instead by the new hubnet reset primitive HubNet now supports receiving non list data types including numbers strings and matrices HubNet Programming Guide revised and expanded all old HubNet primitives removed from language and replaced with new
12. and the color of the turtle itself use set color Note When a turtle s pen is down only the commands forward and back cause drawing Note Theses commands are equivalent to setting the turtle variable pen down to true or false plot plot number Increments the x value of the plot pen by plot pen interval then plots a point at the updated x value and a y value of number The first time the command is used on a plot the point plotted has an x value of 0 Primitives Dictionary 126 NetLogo 1 1 User Manual plot name plot name Reports the name of the current plot a string plot pen down ppd plot pen up ppu plot pen down plot pen up Puts down or up the current plot pen so that it draws or doesn t By default all pens are down initially plot pen reset plot pen reset Clears everything the current plot pen has drawn moves it to 0 0 and puts it down If the pen is a permanent pen the color and mode are reset to the default values from the plot Edit dialog plotxy plotxy number1 number2 Moves the current plot pen to the point with coordinates number1 number2 If the pen is down a line bar or point will be drawn depending on the pen s mode plot x min plot x max plot y min plot y max plot x min plot x max plot y min plot y max Reports the minimum or maximum value on the x or y axis of the current plot These values can be set with the commands set plot x range and set plot
13. exp exp number Reports the value of e raised to the number power Note This is the same as e number Primitives Dictionary 108 NetLogo 1 1 User Manual export output export plot export world export output filename export plot plotname filename export world filename export output writes the contents of the output portion of the Command Center to an external file given by the string filename export plot writes the x and y values of all points plotted by all the plot pens in the plot given by the string plotname to an external file given by the string filename If a pen is in bar mode mode 0 and the y value of the point plotted is greater than 0 the upper left corner point of the bar will be exported If the y value is less than 0 then the lower left corner point of the bar will be exported export world writes the values of all variables both built in and user defined including all observer turtle and patch variables to an external file given by the string filename The result file can be read back into NetLogo with the import world primitive export plot and export world save files in in plain text comma separated values csv format CSV files can be read by most popular spreadsheet and database programs as well as any text editor If the file already exists it is overwritten If you wish to export to a file in a location other than the NetLogo folder you should include the full path to the file you wish t
14. of the maximum value of the variable patch variable of the four patches to the north south east and west of the turtle If there are multiple patches that have the same greatest value a random patch from those patches will be selected See also uphill downhill downhill4 user choice user choice value list of choices Opens a dialog with value displayed as the message and a button corresponding to each item in list of choices Reports the item in ist of choices that is associated with the button the user presses value may be of any type but is typically a string if yes user choice Do you really want to setup the model no yes setup user input user input value Reports the string that a user types into a textbox in a dialog with title value The value may be of any type but is typically a string show user input What is your name user message user message value Opens a dialog with value displayed as the message The value may be of any type but is typically a string user message There are count turtles turtles V Primitives Dictionary 144 NetLogo 1 1 User Manual value from value from agent reporter Reports the value of the reporter for the given agent turtle or patch show value from turtle 5 who who gt 25 show value from patch 0 0 count turtles in radius 3 prints the number of turtles located within a three patch radius of the o
15. 140 itself Below is a chart showing the range of colors you can use in NetLogo black 0 white 9 999 gray 5 8 9 9 999 red 15 18 19 19 999 orange 25 28 29 29 999 brown 35 ae 39 39 999 yellow 45 48 49 49 999 green 55 58 59 59 999 lime 65 68 69 69 999 turquoise 75 78 79 79 999 cyan 85 88 89 89 999 sky 95 98 99 99 999 blue 105 108 109 109 999 violet 115 118 119 119 999 magenta 125 128 129 129 999 pink 135 138 139 139 999 The chart shows that e Some of the colors have names You can use these names in your code e Every named color except black and white has a number ending in 5 On either side of each named color are darker and lighter shades of the color 0 10 20 and so on are all black 9 999 19 999 29 999 and so on are all white Code Example The color chart was made in NetLogo with the Color Chart Example model Note If you use a number outside the 0 to 140 range NetLogo will repeatedly add or subtract 140 from the number until it is in the O to 140 range For example 25 is orange so 165 305 445 and Programming Guide 60 NetLogo 1 1 User Manual so on are orange too and so are 115 255 395 etc This calculation is done automatically whenever you set the turtle variable color or the patch variable pcolor Should you need to perform this calculation in some other context use the wrap color primitive If you want a color that s not on the chart more can
16. 4 of 50 of the chemical from each neighboring patch display display i Resumes updating of the graphics window which may have been turned off using the no display command Any changes in the state of the graphics window that were made while no display was in effect will immediately be drawn on screen all at once See also no display Primitives Dictionary 105 NetLogo 1 1 User Manual distance distance agent Reports the distance to the given turtle or patch Unlike distance nowrap turtles and patches use the wrapped distance around the edges of the screen if that distance is shorter than the on screen distance distance nowrap distance nowrap agent Reports the distance to the given turtle or patch Unlike distance this always reports the on screen distance never a distance that would require wrapping around the edges of the screen distancexy distancexy xcor ycor Reports the distance to the point xcor ycor Unlike distancexy nowrap the wrapped distance around the edges of the screen is used if that distance is shorter than the on screen distance if distancexy 0 0 gt 10 set color green all turtles more than 10 units from the center of the screen turn green distancexy nowrap distancexy nowrap xcor ycor EI Reports the distance to the point xcor ycor Unlike distancexy this always reports the on screen distance never a distance that would require w
17. 53 NetLogo 1 1 User Manual the commands that are entered into the Command Center This area is strictly for reference commands cannot be accessed or changed from this box To clear this box click clear in the top right corner The smaller text box below the large box is where commands are entered On the left of this box is the agent popup menu and on the right is the history popup menu The agent popup menu allows you to select either observer turtles or patches This is an easy way to assign an agent to a command and it is the same as writing ask turtles Note a quicker way to change between observer turtles and patches is to use the tab key on your keyboard The history popup menu lists all of the commands entered that can be accessed and used again The up and down arrow keys on your keyboard will retrieve that last command that was written Note that pressing the clear function clears only the large display box and not the history To clear the history section choose clear history found at the top of its popup menu Procedures Tab This tab is the workspace where the code for the model is stored Commands you only want to use immediately go in the Command Center commands you want to save and use later over and over again are found in the Procedures tab 98 18 2 1 Compile Find Find Again globals ticks breeds sheep wolves turtles own energy sheep own grabbed used to prevent two
18. 70 Firstime NOIUODO USES iaa errada 70 Teacher KOR IODS eeren Sm 71 Getting Started VEI EAMES IN sarria 71 BETIS MEINE IERI OE TEUER LLLI TED 71 mE eH S NI 71 R nno SSA eT E TQ LIS S TR POENI UN 72 Proxy web servers and firewalls circa ii EA EO Re KL FIR LO eR EX Id 72 HubNet Programming CIUIGB a 72 lege m A A 72 A 74 NeiLogo Commands ai pia AN 74 GUT NUI UC e t a 74 AE Was fa pe macs creed ads EE TNCS RES 74 SAI A a m 75 ege 75 Appendix HubNet A EERSTEN 75 unie ACIES LL EDI c See 77 SUM 2 A A D 77 Creating and Editing SRI EE ES el E 78 Behavior Space CUT TOIT TTE 79 ig ERAI gr GTS f nd RR 79 mi AES TOUR 80 internace PROTEC DC OTT 81 SHE VOR a odis en nbl He ia D 81 PEO Di ase pde ue ivi ned Bue bx ICM EN I M TEIL UEM EUM 83 Eyaluatan Ms ri GIAN 83 FAQ Frequently Asked Questi0NS ooomcccccnnnnonccconannnonoconnnonannnnncncncncrnnnnnnnnere rr enne nnne nn nnns nnn nnnm 87 eai ORUM 88 DONOSO RT Umm 89 LIO m A X 90 Prog annie A 91 alui ICONS add 94 CABAS ol PA MUSAS A AA 94 o coni fee RE O d T LE TRE ERR 94 Patch related primitive uei A rai 94 NetLogo 1 1 User Manual Table of Contents Primitives Dictionary create custom turtles cct create custom lt BREED gt cct BREED create Inmporary plol DEB iria ii M Ee PS NetLogo 1 1 User Manual Table of Contents Primitives Dictionary
19. a graphic into NetLogo e My model runs slowly How can speed it up e want to try HubNet Can I e Can run a NetLogo model from the command line Can run it without a GUI Programming e How is the NetLogo language different from the StarLogoT language How do convert my StarLogoT model to NetLogo e The NetLogo world is a torus that is the edges of the screen are connected to each other so turtles and patches wrap around Can use a different world topology bounded infinite plane sphere etc e Does NetLogo have a command like StarLogo s grab command e tried to put at after the name of a variable for example variable at 1 0 but NetLogo won t let me Why not es I m getting numbers like 0 10000000004 and 0 799999999999 instead of 0 1 and 0 8 Why e Is there some simple way to multiply one list by another list or number without writing a procedure e Can read data from a file FAQ Frequently Asked Questions 87 NetLogo 1 1 User Manual How does NetLogo decide when to switch from agent to agent when running code General What is NetLogo written in NetLogo is written entirely in Java version 1 1 How do cite NetLogo in an academic publication NetLogo itself Wilensky U 1999 NetLogo _http ccl northwestern edu netlogo Center for Connected Learning and Computer Based Modeling Northwestern University Evanston IL HubNet Wilensky U Stroup W 1999 HubNet http ccl northwe
20. as moving or creating a turtle or changing the value of an agent variable Setting a local variable doesn t count To prolong an agent s turn use the without interruption command In general we suggest you write your NetLogo code so that it does not depend on a particular scheduling mechanism We make no guarantees that the scheduling algorithm will remain the same in future versions FAQ Frequently Asked Questions 93 Primitives Dictionary Alphabetical AB CDEFGHIJLMNOPRSTUVWX Categories Turtle Patch Agentset Color Control Logic Display HubNet I O List String Math Plotting Special Variables Keywords Constants Categories of Primitives This is an approximate grouping Remember that a turtle related primitive might still be called by patches or observers and vice versa To see which agent turtles patches observer can actually run each command consult each individual entry in the dictionary Turtle related back bk BREED at BREED here clear turtles ct create BREED create custom BHEED create custom turtles cct create turtles crt die distance distance nowrap distancexy distancexy nowrap downhill downhill4 dx dy forward fd hatch hideturtle ht home inspect jump left It myself no label nobody of other turtles here other BHEED here patch here pen down pd pen up pu right rt set default shape setxy shape showturtle st sprout stamp towards towards nowrap towardsxy towardsxy nowrap turtle turtles
21. been using the name of the color This is because NetLogo recognizes 16 different color names This does not mean that NetLogo only recognizes 16 colors There are many shades in between these colors that can be used too Here s a chart that shows the whole NetLogo color space black 0 white 9 999 gray 5 6 7 8 9 9 999 red 15 18 19 19 999 orange 25 28 29 29 999 brown 35 38 39 39 999 yellow 45 48 49 49 999 green 55 EE 59 59 999 lime 65 68 69 69 999 turquoise 75 78 79 79 999 cyan 85 88 89 89 999 sky 95 98 99 99 999 blue 105 108 109 109 999 violet 115 118 119 119 999 magenta 125 128 129 129 999 pink 135 30 131 132 133 138 139 139 999 To get a color that doesn t have its own name you just refer to it by a number instead or by adding or subtracting a number from a name For example when you type set color red this does the same thing as if you had typed set color 15 And you can get a lighter or darker version of the same color by using a number that is a little larger or a little smaller as follows e Choose Patches from the popup menu in the Command Center or use the tab key eType set pcolor red 2 By subtracting from red you make it darker eType set pcolor red 2 By adding to red you make it lighter Tutorial 2 Commands 30 NetLogo 1 1 User Manual You can use this technique on any of the colors listed in the chart Agent Monitors and Agent Commanders In the previ
22. colors and have headings from 0 to 360 evenly spaced The new turtles immediately run commands This is useful for giving the new turtles a different color heading or whatever breeds canaries snakes Primitives Dictionary 103 NetLogo 1 1 User Manual to setup ca create custom canaries 50 set color yellow create custom snakes 50 set color green end Note While the commands are running no other agents are allowed to run any code as with the without interruption command This ensures that the new turtles cannot interact with any other agents until they are fully initialized In addition no screen updates take place until the commands are done This ensures that the new turtles are never drawn on screen until they are fully initialized create tem porary plot pen create temporary plot pen string A new temporary plot pen with the given name is created in the current plot and set to be the current pen Few models will want to use this primitive because all temporary pens disappear when clear plot or clear all plots are called The normal way to make a pen is to make a permanent pen in the plot s Edit dialog If a temporary pen with that name already exists in the current plot no new pen is created and the existing pen is set to the the current pen If a permanent pen with that name already exists in the current plot a runtime error is thrown The new temporary plot pen has the following initial settings e
23. comfortable with If the individual is in a group that has a higher percentage of people of the opposite sex than their tolerance allows then they become uncomfortable and leave the group to find another group For example if the tolerance level is set at 25 then males are only comfortable in groups that are less than 25 female and females are only comfortable in groups that are less than 25 male As individuals become uncomfortable and leave groups they move into new groups which may cause some people in that group to become uncomfortable in turn This chain reaction continues until everyone at the party is comfortable in their group Note that in the model tolerance is not fixed You the user can use the tolerance slider to try different tolerance percentages and see what the outcome is when you start the model over again How to start over 1 If the go button is pressed black then the model is still running Press the button again to stop it 2 Adjust the tolerance slider to a new value by dragging its red handle 3 Press the setup button to reset the model 4 Press the go button to start running again Challenge As the host of the party you would like to see both men and women mingling within the groups Adjust the tolerance slider on the side of the Graphics Window to get all groups to be mixed as an end result To make sure all groups of 10 have both sexes at what level should we set t
24. environment is fairly simple a black background with a white street and number of blue cars and one red car Changes that could be made to the model include changing the color and shape of the cars adding a house or street light creating a stop light or even creating another lane of traffic Some of these suggested changes are cosmetic and would enhance the look of the model while the others are more behavioral We will be focusing more on the simpler or cosmetic changes throughout most of this tutorial Tutorial 3 will go into greater detail about behavioral changes which require changing the Procedures tab To make these simple changes we will be using the Command Center The Command Center The Command Center is located in the Interface Tab and allows you to enter commands or directions to the model without changing the actual mechanisms of the model Commands are instructions you can give to NetLogo s agents turtles patches and the observer Tutorial 2 Commands 26 NetLogo 1 1 User Manual In Traffic Basic e Press the setup button e Locate the Command Center e Click the mouse in the white box at the bottom of the Command Center e Type the text shown here Command Center Clear e Press the return key Refer to the Interface Guide for details explaining the different parts of the Command Center What happened to the Graphics Window You may have noticed the background of the Graphics Windo
25. have general feedback suggestions or questions write to feedback ccl northwestern edu Reporting Bugs If you would like to report a bug that you find in NetLogo write to bugs ccl northwestern edu When submitting a bug report please try to include as much of the following information as possible A complete description of the problem and how it occurred e The NetLogo model or code you are having trouble with If possible attach a complete model e Your system information NetLogo version OS version and so on This information is available from NetLogo s About NetLogo menu item e Any error messages that were displayed Contacting Us 12 Sample Model Party This activity is designed to get you thinking about computer modeling and how you can use it It also gives you some insight into the NetLogo software We encourage beginning users to start with this activity At a Party Have you ever been at a party and noticed how people cluster in groups You may have also noticed that people do not stay within one group but move throughout the party As individuals move around the party the groups change If you watched these changes over time you would notice patterns forming For example in social settings people tend to exhibit different behavior than when they are at work or home Individuals who are confident within their work environment may become shy and timid at a social gathering And others who are quiet and res
26. member position remove remove duplicates replace item reverse sentence sort values from String primitives position remove read from string replace item reverse substring word Mathematical primitives Arithmetic Operators 4 mean median min mod pi precision random random seed round sin sqrt standard deviation sum tan variance Plotting primitives autoplot auto plot off auto plot on clear all plots clear plot create temporary plot pen export plot histogram histogram list plot plot name plot pen down ppd plot pen reset plot pen up ppu plot x max plot x min plot y max plot y min plotxy ppd ppu set current plot set current plot pen set histogram num bars set plot pen color set plot pen interval set plot pen mode set plot x range set plot y range Predefined Variables Turtles breed color heading hidden label label color pen down shape Primitives Dictionary 95 NetLogo 1 1 User Manual size who read only xcor ycor Patches plabel color pxcor pycor patches own to to report turtles own Constants Mathematical Constants e 2 718281828459045 pi 3 141592653589793 Boolean Constants false true Color Constants The allowable range of values for colors is O up to but not including 140 Each color ranges from black to white over a scale of ten Thus the color red goes from black 10 to dark red 11 to red 15 to light red 19 to white 19 9 The scale is discontinuou
27. of multiple number variables Constant Lists You can make a list by simply putting the values you want in the list between brackets like this set mylist 2 4 6 8 Note that the individual values are separated by spaces You can make lists that contains numbers and strings this way as well as lists within lists for example 2 4 3 STE The empty list is written by putting nothing between the brackets like this Building Lists on the Fly If you want to make a list in which the values are determined by reporters as opposed to being a series of constants use the List reporter The list reporter accepts two other reporters runs them and reports the results as a list If wanted a list to contain two random values might use the following code set random list list random 10 random 20 This will set random list to a new list of two random numbers each time it runs To make longer lists use the 1ist reporter with the sentence reporter which concatenates two lists combines their contents into a single larger list Programming Guide 66 NetLogo 1 1 User Manual The_values from primitive lets you construct a list from an agentset It reports a list containing the each agent s value for the given reporter The reporter could be a simple variable name or a more complex expression even a call to a procedure defined using to report A common idiom is max values from turtles sum values from turtles a
28. range The wrapping is done by repeatedly adding or subtracting 140 from the given number until it is in the 0 to 140 range This is the same wrapping that is done automatically if you assign an out of range number to the color turtle variable or pcolor patch variable show wrap color 150 10 show wrap color 10 130 X xor boolean xor boolean2 Reports true if either boolean or boolean2 is true but not when both are true if pxcor gt 0 xor pycor gt 0 set pcolor blue upper left and lower right quadrants turn blue Primitives Dictionary 147
29. reopen it Component descriptions Sliders list The current list of sliders in the model which is updated automatically as sliders are added changed or deleted The values specified to the right of each slider are the current values that slider is assigned to take in the experiment Change values button Brings up the Slider values dialog so you can change slider values Slider values dialog The dialog that pops up when the change values button is pushed e To specify values in a list enter the values in the upper text field Values in the list can be separated by one or more spaces commas tabs or semicolons BehaviorSpace Guide 81 NetLogo 1 1 User Manual To specify values in a range enter the first and last values the slider should take and the increment by which to traverse this range e First and last values of a range are inclusive e The first value must be less than or equal to the last one e The increment must be greater than zero e If a single value is entered more than once then each instance will be treated as a separate value that is if a particular slider has four 5 s then that slider will have the value 5 four times e To leave the dialog there must be valid values in both the list and range text fields e The values used for a particular slider in an experiment will be those whose checkbox is currently selected For example if the values range checkbox is selected then the values specified by the r
30. t stop until every turtle or patch stops a single turtle or patch doesn t have the power to stop the whole button substring substring string position1 position2 Reports just a section of the given string ranging between the given positions Note The positions are numbered beginning with 0 not with 1 show substring turtle 1 4 gt urt sum sum list Reports the sum of the elements in the list show sum values from turtles energy 77 prints the total of the variable energy Primitives Dictionary 139 NetLogo 1 1 User Manual from all the turtles T tan tan number Reports the tangent of the given angle Assumes the angle is given in degrees timer timer Reports the current value of the global clock since the command reset timer was last run The resolution of the clock is milliseconds Whether it is accurate to the nearest millisecond may vary from system to system to to procedure name to procedure name input1 input2 Used to begin a command procedure to setup ca crt 500 end to circle radius cct 100 fd radius end to report to report procedure name to report procedure name input1 input2 Used to begin a reporter procedure The body of the procedure should use report to report a value for the procedure See report to report average a b report a b 2 end to report absolute value number ifelse number gt 0 report number repor
31. the basis of a commercial software or hardware product without first obtaining appropriate licenses from Uri Wilensky We make no representations about the suitability of this software for any purpose It is provided as is without express or implied warranty We are in the process of reevaluating the language of the license in response to user feedback In the near future we intend to send out a revised license Is the source code to NetLogo available At present no We are evaluating how best to distribute NetLogo when it is in a more mature state Making the source available is one possibility FAQ Frequently Asked Questions 88 NetLogo 1 1 User Manual We do understand however that it is important that NetLogo not be a closed and non extensible platform That is not our intention for the product For a future version of NetLogo we plan to add an API so that users can add their own extensions to NetLogo We d like to work with interested users to help design this API to suit the needs of our user community Do you offer any workshops or other training on NetLogo From time to time Contact us at feedback ccl northwestern edu if interested Has anyone written a model of x The best place to ask this question is on the NetLogo Users Group You should also check the NetLogo User Community Models section of our Models Library web page What s the difference between StarLogo MacStarLogo StarLogoT and NetLogo The first v
32. to try different values Maybe one time you ll want the turtles to try and solve a hard world and maybe another time you ll just want to look at an easy landscape So we ll make a slider variable Create a slider in the Interface Window and call it smoothness in the editing box The minimum can be 0 and the maximum can be 50 or so Then change your code to repeat smoothness diffuse elevation 1 Experiment with the turtles performance in different worlds We still haven t even begun to solve the greedy search problem though Before trying something else it d be nice if we could have some other more precise method for evaluating the turtles performance watching little arrows writhe about in the Graphics Window only helps so much Fortunately NetLogo allows us to plot data as we go along Tutorial 43 Procedures 43 NetLogo 1 1 User Manual To make plotting work we ll need to create a plot in the Interface tab and set some settings in it Then we ll add one more procedure to the Procedures tab which will update the plot for us Let s do the Procedures tab part first Change go to call the new procedure we re about to add to go move turtles do plots end Then add the new procedure to do plots set current plot Turtles at Peaks plot count turtles with elevation gt highest 100 end What we re plotting is the number of turtles who ve reached our peak zone within 1 of the highest elevation at some g
33. turtles to wander around each trying to get to the patch that has the highest elevation Let s try a simple i e naive algorithm first We ll assume a three things 1 that the turtles cannot see ahead farther than just one patch 2 that each turtle can move only one square each turn and 3 that turtles are blissfully ignorant of each other Before we had a procedure move turtles like this to move turtles ask turtles set heading random 360 fd 1 Tutorial 3 Procedures 41 NetLogo 1 1 User Manual end But now we don t want them to move randomly about We want each turtle to look at the e evation of each patch around it and move to the patch with the highest elevation i e execute a greedy search if you will If none of the patches around it have a higher elevation than the patch it is on it ll stay put Here s the code performs a greedy search of radius 1 for highest elevation to move to local max Call this procedure from go ask turtles set heading uphill elevation if elevation of patch at dx dy elevation fd 1 J end There are five new commands here uphill elevation of patch at and dx and dy uphill elevation finds the heading to the patch with the highest value of elevation in the patches in a one patch radius of the turtle Then through the use of the command set heading the turtle sets its heading to that direction elevation of patch at dx dy ha
34. web browser must support Java In addition you must have Java enabled in the browser s preferences or settings The applet has been tested to work in the following environments Windows 95 NT 98 ME 2000 XP e Microsoft Internet Explorer minimum version 5 Netscape minimum version 6 Macintosh OS X e Mac OS X 10 1 3 version or higher required e Internet Explorer browser 5 1 or higher works e Netscape and Mozilla may work if you use MRJPluginCarbon e other browsers not tested Macintosh OS 8 x or 9 x e JVM Apple s Macintosh Runtime for Java MRJ 2 2 5 2 2 3 and 2 2 4 will probably also work Microsoft Internet Explorer minimum version 4 5 but version 5 is recommended and for HubNet users it is required e Netscape minimum version 6 Other Java enabled OS Linux Solaris et al We have not tested this option ourselves but some users have reported success If if it doesn t work for you please let us know If it doesn t work you may also try downloading the application instead System Requirements 9 Known Issues If NetLogo malfunctions please send us a bug report See the Contact Us section for instructions Known bugs all systems e The Turtle Sizes and Exact Turtle Positions features can cause display anomalies under some circumstances e Integers in NetLogo cannot be larger than 2 31 and if you exceed this range instead of a runtime error occurring you get incorrect results e
35. y range Their default values are set from the plot Edit dialog Primitives Dictionary 127 NetLogo 1 1 User Manual position position item list position string1 string2 On a list reports the first position of tem in list or false if it does not appear On strings reports the position of the first appearance string1 as a substring of string2 or false if it does not appear Note The positions are numbered beginning with 0 not with 1 Suppose mylist is 2 7 4 7 Bob show position 7 mylist gt 1 show position 10 mylist false show position rin string gt 2 See also member precision precision number places Reports number rounded to places decimal places If places is negative the rounding takes place to the left of the decimal point show precision 1 23456789 3 gt 1 235 show precision 3834 3 gt 4000 print print value Prints value in the Command Center followed by a carriage return The calling agent is not printed before the value unlike show See also show type R Primitives Dictionary 128 NetLogo 1 1 User Manual random random number If number is positive reports a random number greater than or equal to 0 but strictly less than number If number is negative the number reported is less than or equal to 0 but strictly greater than number If number is zero the result is always zero as well If number is an integer reports a random integer I
36. 1 e Mac OS X support in Classic environment Models Library organized into categories with screen shots e language now supports turtle breeds e BehaviorSpace a tool for exploring the space of different ways a model can behave e Export World Export Plot and Export Output local variables locals keyword e Find and Find Again buttons in Procedures window e HubNet can now send data to the teacher calculator e miscellaneous fixes and improvements Beta 5 June 2001 e models run much faster now e collection of Code Examples added to Models Library e agent monitors much improved e miscellaneous fixes and improvements Beta 4 March 2001 e greatly improved general stability amp reliability e web based installer automates installation process e runs as stand alone application on all platforms e shapes editor for turtle shapes e miscellaneous fixes and improvements Beta 3a December 2000 e miscellaneous fixes and improvements Beta 2 October 2000 e miscellaneous fixes and improvements Beta 1 September 2000 e first public beta release What s New System Requirements NetLogo is designed to run almost any type of computer but you may experience problems with older less powerful systems or older versions of system software The exact requirements are summarized below If you have any trouble with NetLogo not working on your system we would like to offer assistance Please write bug
37. 1 User Manual e The grid has a maximum height and width which is reached when there are more than 5 squares in either direction and cannot be resized e Squares turn gray when there is insufficient information to construct a grid this happens when either axis has not been assigned a slider one axis is sufficient if a model only has one slider Set of sliders components held constant These sliders consist of all those not present as axes of the fitness landscape Since all the model runs represented on the landscape have the same value for these sliders namely the one currently selected on the slider components they are considered held constant for the landscape By changing the value of a single one of these sliders the whole landscape changes because it now represents a whole new set of runs If you changed a slider from 10 to 12 say then all the runs in which that slider had the value 10 are replaced by those in which it had the value 12 e Changing the value of these sliders does not affect the value of the sliders on the main interface e The only values the sliders can take are those that they actually had in the experiment Behavior plot Displays the data from individual runs as you move the mouse over their corresponding squares on the fitness landscape It s x axis is time clicks and its y axis is behavior that is the value reported by the behavior reporter entered in the setup window e The best fit line o
38. 4 5 gt 5 forward fd forward number The turtle moves forward by number steps If number is negative the turtle moves backward Turtles using this primitive can move a maximum of one unit per time increment So fd 0 5 and fd 1 both take one unit of time but fd 3 takes three See also_jump Primitives Dictionary 110 NetLogo 1 1 User Manual fput fput item list Adds item to the beginning of a list and reports the new list Suppose mylist is 5 7 10 set mylist fput 2 mylist mylist is now 2 5 7 10 G globals globals var1 var2 This keyword like the breeds lt BREED gt own patches own and turtles own keywords can only be used at the beginning of a program before any function definitions It defines new global variables Global variables are global because they are accessible by all agents and can be used anywhere in a model Most often globals is used to define variables or constants that need to be used in many parts of the program H hatch hatch number commands Each turtle creates number new turtles each identical to itself and tells the new turtles to run commands This is useful for giving the new turtles different colors headings breeds or whatever Note While the commands are running no other agents are allowed to run any code as with the without interruption command This ensures that the new turtles cannot interact with any other agents until they are fully initia
39. 9 The Primitives Dictionary has a section that lists of all the list related primitives Strings To input a constant string in NetLogo surround it with double quotes Programming Guide 67 NetLogo 1 1 User Manual The empty string is written by putting nothing between the quotes like this Most of the list primitives work on strings as well butfirst string gt tring butlast string gt strin empty gt true empty string gt false first string gt s item 2 string gt r last string gt g length string gt 6 member s string gt true member rin string gt true member ron string gt false position s string gt 0 position rin string gt 2 position ron string gt false remove r string gt sting remove s strings gt tring replace item 3 String o gt strong reverse string gt gnirts A few primitives are specific to strings such as is string substring and word is string string gt true is string 37 gt false substring string 2 5 gt rin word tur tle gt turtle Strings can be compared using the gt lt and gt operators To concatenate strings that is combine them into a single string you may also use the plus operator like this tur Lie gt turtle If you need to embed a special character in a string use the following escape sequences
40. E POSCIT HER sees 116 T T I 116 je EE 116 Me ahs sae aera SLM UID n MSS M IE M DIM Ma EMI E 117 Fy Uren E E meee d Ui LEE M E 117 A De vU O E 117 I O O M 117 e 117 a c T 117 E park SHE DURER HUE ORC A AN REN ED ARI E cEOS ITEM A 000 118 llla RECTE 118 ER TU CU E TEES 118 ein ct ME MN M I 118 EE 119 E eet eee M PELA E LM EI EE MM M LE I E 119 i 119 t 119 ULT HTTP 119 FU PN c e Lp csc ee P LI M E PM ALD I E CM MEI 119 nE orum Tues m EUM 120 o EUM ni M M E AM E 120 MAN DOTT 120 IM ake tu ML D E uU ME Uu LE UU E A 120 gll Ee e reina ici 121 A A Ae D ANR E Ae mE 121 ONS KE 121 TOOLS Se COT WOU aay ouai oie ib 121 AI RTT ETT 122 m CES 122 neighbors EE EIU C TRETEN 122 PN S Dies o E uu EE ML I IMP dace ne IE iM e TM le 122 A EAE ATEA E ATE A A A 123 DEE 123 MINE 123 DREES 123 a EE 124 A dI ee i i M M 124 ELE AE GE 124 IB e E 124 other turtles here other BREED herB coocncccccnnocncccnnnccnnnnnncnonononannnononanonononaninonono 124 mc A MP 125 EEE oii sion OE OUR A E 125 Eus uite ee AA OP det MU MM IM M 125 IS LM m o A 125 A abt oai MM MM EM 126 HIM mI RET T TOT TC TTE ii 126 Ime SEES pen up UU NN a 126 vi NetLo
41. ML comments saved applets now bring up runtime error dialogs on all systems when something goes wrong What s New 3 NetLogo 1 1 User Manual saved applets now work when run from the local hard drive as opposed to a web server even on Mac OS X and even on Windows if the model name has spaces in it Version 1 1 July 2002 e content added Frequently Asked Questions section to User Manual new suite of 1 dimensional cellular automata models Cellular Automata 1D an improved version of our old Cellular Automata model CA 1D Totalistic CA 1D Rule 30 CA 1D Rule 30 Turtle CA 1D Rule 90 CA 1D Rule 110 CA 1D Rule 250 new model conversions Koch Curve Rumor Mill Random Walk Left Right new chemistry models Crystallization Moving Crystallization Directed improved models Crystallization Basic formerly Solidification Mouse Example expanded Tetris bugfixes Pac Man bugfixes AIDS bugfix cleanup clearer code Traffic 2 Lanes cleanup clearer code e features Save as Applet on the File menu lets you embed your model in any web page you can now print the contents of any tab on a printer Procedures tab now has popup menu that lets you instantly jump to any procedure in your code Interface tab is now scrollable Interface tab now has contextual popup menus that let you create edit and delete interface elements as well as open turtle and patch monitors on Macs control click to bring up the menus
42. NetLogo allows for the same functionality with the new agentset syntax Known Issues 10 NetLogo 1 1 User Manual eifelse report maxint minint maxnum minnum e import turtles import patches import turtles and patches note that NetLogo adds import world though beep get date and time readlist yes or no e miscellaneous seldom used plotting reporters such as plot pencolor pp plotlist pp plotpointlist ppinterval ppxcor ppycor etc ebit bitand bitneg bitor bitset bitstring bitxor make bitarray rotate left rotate right shift left shift right random exponential random exponential list random normal random normal list random poisson random poisson list random uniform random uniform list distribute random exponential distribute random poisson e close movie open movie setup movie movie snapshot snapshot e load pict save pict e camera brightness camera click camera init camera set brightness e choose directory dialog choose file dialog choose new file dialog netlogo directory project directory project name project pathname save project Known Issues 11 Contacting Us Feedback from users is very valuable to us in designing and improving NetLogo We d like to hear from you Website Our website at_ccl northwestern edu includes our mailing address and phone number It also has information about our staff and our various research activities Feedback Questions Etc If you
43. On some Java virtual machines when you print the Interface tab there may be pieces missing and or extra artifacts e Out of memory conditions are not handled gracefully Macintosh only bugs e The Help menu has an extra blank item in it e When running in Classic under versions of Mac OS X prior to 10 2 the User Manual item on the Help menu will launch a Classic browser instead of a native browser unless a native browser is already running Linux UNIX only bugs e Resizing and moving of items in the Interface tab may function erratically on some systems e Saved applets may not work correctly in Netscape version 4 Planned features This is a partial list of features we are working on currently We plan to continue to improve NetLogo Periodically new versions will be available from our web site e Java API for user defined extensions to NetLogo e Improved engine so models run faster e Optional randomized agent scheduler e Adjusting the execution speed of a model as it runs without adding a slider and modifying your code e Ability to have multiple models open e Making a QuickTime movie of your model e Improved support for HubNet e Native Mac OS X support note we already run well under OS X in Classic mode Unimplemented StarLogoT primitives The following StarLogoT primitives are not available in NetLogo Note that many StarLogoT primitives such as count turtles with are intentionally not included in this list because
44. Pen down e Color black e Mode 0 line mode e Interval 1 0 Note that the old primitive set plot pen which was used in earlier versions of NetLogo is now just an alternate name for this primitive set plot pen is available only for reasons of compatibility new models should not use set plot pen See clear plot clear all plots and set current plot pen D die die x The turtle dies if xcor 20 die Primitives Dictionary 104 NetLogo 1 1 User Manual all turtles with xcor greater than 20 die See also ct diffuse diffuse patch variable number is Tells each patch to share number 100 percent of the value of patch variable with its eight neighboring patches number should be between 0 and 1 Note that this is an observer command only even though you might expect it to be a patch command The reason is that it acts on all the patches at once patch commands act on individual patches diffuse chemical 0 5 each patch diffuses 50 of its variable chemical to its neighboring 8 patches Thus each patch gets 1 8 of 50 of the chemical from each neighboring patch diffuse4 diffuse4 patch variable number i Like diffuse but only diffuses to the four neighboring patches to the north south east and west not to the diagonal neighbors diffuse4 chemical 0 5 each patch diffuses 50 of its variable chemical to its neighboring 4 patches Thus each patch gets 1
45. Procedures 44 NetLogo 1 1 User Manual Turtles at Peaks 49 5 3 E 0 0 0 0 Time You might try running the model several times under different settings i e different values of smoothness and watch how fast the plot converges to some value and what fraction of the turtles make it to the top Some More Details There are a few miscellaneous bugs and quirks you might have already noticed Here are some quick changes you can make First we have a green landscape a naturally green turtle is going to be hard to see In the ask turtles block in setup turtles you can say if color green set color red Second instead of always using 100 turtles you can have a variable number of turtles Make a slider variable say number e Editing Slider Minimum go Increment 1 Maximum 99 Value 99 Units optional Then instead of crt 100 you can type crt number How does using more or fewer turtles affect the success value displayed by the plot Third when all the turtles have found their local maxima wouldn t it be nice for the model to stop This requires a few lines of code e Add a global variable turtles moved to the globals list globals highest maximum patch elevation Tutorial 43 Procedures 45 NetLogo 1 1 User Manual lowest minimum patch elevation turtles moved so we know when to stop the model e At the end of the go procedure add a test to se
46. TOR re SA NetLogo 1 1 User Manual NetLogo 1 1 User Manual Table of Contents LI ET ri AS 1 c ETT 1 PRIEST EI E UTIMS 3 Version 1A EAU 2002 P ei E 3 IEA A 4 Version 1O Api 2002 A AAA AS EN AAA ANA 6 A A AT 6 AE ETT 6 A KEE 6 Beia PARTS O01 NN 6 Beta 6 August 2001 Laia ii ei dedicas 7 A O Z EE A RE 7 ARA ENEE hee 7 pi 2UUO e ee EE Te ie elec LE aS DLE A aE eens cee ele ELM E 7 EC CD NNI T System Heguiremmeiis A A iii 8 PRESA l0 EU eerie nln Seely AR N miner ter err 8 System Requirements AICA ae 8 o C EUM 8 Mitin iaa Bal ave laa da caved FERE TEE YET E CARRETERA dd 8 cali EE 8 Oher PISOS eae as th p pte iaa 9 System Regu uremstiis E LIT 9 Windows 95 MT 95 ME 2700 XP ona ada 9 Macintosh A donde bel M Mibi A ID pr EL 9 MEA RC IM A ERN RE 9 Other Java enabled OS Linux Solaris et ali 9 ee EI INTTR 10 Koown Bugs A A 10 Eieren el 10 CUISINE EN 10 A RITE ON T IS 10 Unimplemented StarLogoT DIES usan 10 Erol i NITE 12 E 12 Feedback Guesta a Elina a aca x E Ree ES 12 al A E 12 cl o GE 13 OU Ea Gilet TT 13 E i dicti uc E E A E E E E E E E EA 15 Thinking Win et d A 16 O EE EE 16 NetLogo 1 1 User Manual Table of Contents BL ld LE MODOS usina pit n 17 Sample Model Wolf Sheep Pre ANG iii 17 Canirelling ihe Modal BUNOS asses EEPROROHARL GERI EE A RARE AA 18 Adjusting Settings Sliders and Gwitche
47. This idea of emergent phenomena can be applied to almost any subject What other emergent phenomena can you think of To see more examples and gain a deeper understanding of this concept and how NetLogo helps learners explore it you may wish to explore NetLogo s Models Library It contains models that demonstrate these ideas in systems of all kinds For a longer discussion of emergence and how NetLogo helps learners explore it see_ Modeling Nature s Emergent Patterns with Multi agent Languages Wilensky 2001 What s Next The section of the User Manual called_Tutorial 1 Running Models goes into more detail about how to use the other models in the Models Library If you want to learn how to explore the models at a deeper level Tutorial 2 Commands will introduce you to the NetLogo modeling language Eventually you ll be ready for Tutorial 3 Procedures where you can learn how to alter and extend existing models to give them new behaviors and build your own models Sample Model Party 16 Tutorial 1 Models If you read the Sample Model Party section you got a brief introduction to what it s like to interact with a NetLogo model This section will go into more depth about the features that are available while you re exploring the models in the Models Library Sample Model Wolf Sheep Predation We ll open one of the Sample Models and explore it in detail Let s try a biology model Wolf Sheep Predation a predator prey
48. a semicolons can be added for visual effect sentence se sentence value value2 Makes a list out of the values If either value is a list its elements are included in the result directly rather than being included as a sublist Examples make this clearer show sentence 1 2 gt 1 2 show sentence 1 2 3 gt 1 2 3 show sentence 1 2 3 gt 1 2 3 show sentence 1 2 3 4 gt 1 2 3 4 set set variable value Sets variable to the given value Variable can be any of the following e An global variable declared using globals e The global variable associated with a slider or switch e A variable belonging to the calling agent e If the calling agent is a turtle a variable belonging to the patch under the turtle e An expression of the form VARIABLE of agent Primitives Dictionary 134 NetLogo 1 1 User Manual set current plot set current plot plotname Sets the current plot to the plot with the given name a string Subsequent plotting commands will affect the current plot set current plot pen set current plot pen penname The current plot s current pen is set to the pen named penname a string If no such pen exists in the current plot a runtime error occurs set default shape set default shape turtles string set default shape breed string i Specifies a default initial shape for all turtles or for a particular breed When a turtle is created or it changes breeds it shape is set to the
49. ands 34 Tutorial 3 Procedures In Tutorial 2 you learned how to use agent monitors and command centers to inspect and modify agents and make them do things Now you re ready to learn about the real heart of a NetLogo Model the Procedures tab This tutorial leads you through the process of building a complete model built up stage by stage with every step explained along the way Setup and Go To start a new model select New from the the File menu Then begin making your model by creating a once button called setup Here s how to make the button 1 click on the button icon in the Toolbar 2 click where you want the button to be in the empty white area of the Interface tab 3 when the dialog box for editing the properties of the button opens type setup in the box labeled Code sup P setu m e Editing Button Ask Observer re Display Name setup Code 1 Forever A gt Co gt A 4 Cancel e 4 press OK to dismiss the dialog box Now you have a button called setup It will execute the procedure setup when pressed which once we define it will do just that set up the NetLogo world the way we want it At this point the Errors tab will turn red That s because there is no procedure called setup If you want to see the actual error message switch to the Errors tab Tutorial 43 Procedures 35 NetLogo 1 1 User Manual 99 8 7 L 3
50. ange will be used not those in the list Behavior reporter text area A place to enter a NetLogo reporter to specify what kind of data is to be collected during each model run This reporter is evaluated before every time click or call to the forever button and once at the end of the run and its value is recorded for later analysis e Input must be a valid NetLogo reporter e Can use any reporters whether built into the NetLogo language or written in the model e lt must report a number Example If you are interested in the population of sick people in the Virus model you might want your behavior reporter to report how many sick people there currently are in the model with the following behavior reporter count people with sick Or if you are investigating the distance between each turtle and the center of the screen in Turtles Circling you might have it report the mean of all the turtle s distances to the center mean values from turtles distancexy 0 0 Time clicks checkbox and text field When the checkbox is selected each model run will end after the number of time clicks specified in the text field One time click means one push or iteration of the forever button e Input to the text field must be a valid integer not just any numeric reporter Exit condition checkbox and text field When the checkbox is selected each model run will continue until the reporter entered in the text field reports true This reporter
51. ar at the beginning of the procedure before any commands A local variable may not have the same name as an existing observer turtle or patch variable See to and to report to hunt turtle procedure locals prey set prey random one of other turtles her if prey nobody eat prey end Primitives Dictionary 118 NetLogo 1 1 User Manual log log number base Reports the logarithm of number in base base show log 64 2 gt 6 See also In loop loop commands Runs the list of commands forever or until the current procedure exits through use of the stop command or the report command Note In most circumstances you should use a forever button in order to repeat something forever The advantage of using a forever button is that the user can click the button to stop the loop Iput Iput value list Adds value to the end of a list and reports the new list Suppose mylist is 2 7 10 Bob set mylist lput 42 mylist mylist now is 2 7 10 Bob 42 max max list Reports the maximum number value in the list It ignores other types of items show max values from turtles xcor ji prints the x coordinate of the turtle which is farthest right on the screen max one of max one of agentset reporter Reports the agent in the agentset that has the highest value for the given reporter show max one of patches count turtles here Primitives Dictionary 119 NetLogo 1 1 User Manual 7 p
52. ask command but also hatch values from value from with min one of max one of and histogram ask turtles ask patches in radius 3 set pcolor color of myself 7 each turtle makes a colored splotch around itself See the Myself Example code example for more examples N neighbors neighbors4 neighbors neighbors4 x Reports an agentset containing the 8 surrounding patches neighbors or 4 surrounding patches neighbors4 show sum values from neighbors count turtles here prints the total number of turtles on the eight 77 patches around the calling turtle or patch ask neighbors4 set pcolor red turns the four neighboring patches red no display no display y Turns off all updating of the graphics window until the display command is issued This has two major uses One your model will run faster when graphics updating is off so if you re in a hurry this command will let you get results faster Two you can control when the user sees screen updates You might want to change lots of things on the screen behind the user s back so to speak then make them visible to the user all at once See also_display Primitives Dictionary 122 NetLogo 1 1 User Manual no label no label This is a special value used to remove labels from turtles and patches When you set a turtle s label to no label or a patch s plabel to no label then a label will no longer be drawn on top of the turtle or patch
53. atches with your mouse by clicking and dragging in the Graphics Window The Graphics Window provides an easy way to open a turtle monitor or patch monitor Just control click Macintosh or right click other OS on the turtle or patch you want to inspect and choose inspect turtle or inspect patch from the popup menu Turtle and patch monitors can also be opened from the Tools menu or by using the inspect command There are a number of settings associated with the Graphics Window You can change these settings by editing the Graphics Window as described in the Working With Interface Elements section above Here are the settings for the Graphics Window Interface Guide 52 NetLogo 1 1 User Manual e Editing Graphics E Screen Edge Y 17 Patch Size pixels 9 0 Font Size of turtle and patch labels 10 ka Turtle Shapes Turtle Sizes experimental 1 Exact Turtle Positions experimental F Cancel gt Apply gt OK To change the size of the Graphics Window adjust the Patch Size setting which is measured in pixels This does not change the number of patches only how large the patches appear on the screen To change the number of patches alter the Screen Edge X and Screen Edge Y settings Note that changing the numbers of patches requires rebuilding the NetLogo world you will lose all turtles and the values of all variables In most NetLogo models every turtle is always the sam
54. be 20 or so It then takes this number and goes fd short for forward that number of step in the direction of its heading end ends the definition of the setup procedure Press your setup button when you ve written the code You will see the turtles quickly spread out in a rough cluster Tutorial 43 Procedures 36 NetLogo 1 1 User Manual Notice the density distribution of the turtles on the Graphics Window Press setup a couple more times and watch how the turtles arrangement changes Can you think of other ways to randomly distribute the turtles over the screen There are lots of ways Note that if a turtle moves off the screen it wraps that is comes in the other side When you re satisfied that the button does what you want it s time to write your next procedure Make a forever button called go Again begin by creating a button but this time check the forever checkbox in the edit dialog e Editing Button Ask Observer Display Name go Code MA Forever lt A gt K Cancel Then write its procedure to go move turtles end Tutorial 3 Procedures 37 NetLogo 1 1 User Manual But what is move turtles s it a primitive built in to NetLogo like fd is No it s a procedure that you re about to write right after the go procedure to move turtles ask turtles rt random 360 fd 1 end Line by line ask turtles says that each turtle should execute the co
55. be found between the integers For example 26 5 is a shade of orange halfway between 26 and 27 This doesn t mean you can make any color in NetLogo the NetLogo color space is only a subset of all possible colors A fixed set of discrete hues is available and you can either decrease the brightness darken or decrease the saturation lighten of those hues to get your desired color but you may not decrease both the brightness and saturation There are a few primitives that are helpful for working with color shades The scale color primitive is useful for converting numeric data into colors And shade o will tell you if two colors are shades of the same basic hue For example shade of orange 27 is true because 27 is a lighter shade of orange Code Example Scale color Example shows you how to use the scale color reporter For many models the NetLogo color system is a convenient way of expressing colors But sometimes you d like to be able to specify colors the conventional way by specifying HSB hue saturation brightness or RGB red green blue values The hsb and rgb primitives let you do this ext ract hsb and extract hsb let you convert colors in the other direction Since the NetLogo color space doesn t include all hues hsb and rgb can t always give you the exact color you ask for but they try to come as close as possible Code Example You can use the HSB and RGB Example model to experiment with the HSB and RGB color sys
56. bnet set tags L1 LOCS looks for the calculator lists L1 and LOCS on the server See the HubNet Programming Guide for details if if condition commands If condition reports true runs commands if xcor 0 set color blue turtles on the right half of the screen turn blue ifelse ifelse reporter commande commands2 Reporter must report a boolean true or false value If reporter reports true runs commands If reporter reports false runs commands2 The reporter may report a different value for different agents so some agents may run commands1 while others run commands2 ask patches ifelse pxcor gt 0 set pcolor blue set pcolor red the left half of the screen turns red and the right half turns blue import world import world filename Reads the values of all variables for a model both built in and user defined including all observer turtle and patch variables from an external file named by the given string The file should be in the format used by the export world primitive Note that the functionality of this primitive is also directly available from NetLogo s File menu When using import world to avoid errors perform these steps in the following order 1 Open the model from which you created the export file 2 Press the Setup button to get the model in a state from which it can be run Primitives Dictionary 115 NetLogo 1 1 User Manual 3 Import the fi
57. c Follow this link for more information NetLogo is the next generation of the series of multi agent modeling languages that started with StarLogo It builds off the functionality of our product StarLogoT and adds significant new features and a redesigned language and user interface NetLogo is written in Java so it can run on any operating system Mac Windows Linux et al It can be run as a standalone application or as an applet within a web browser Features You can use the chart below to help familiarize yourself with the new features NetLogo has to offer StarLogoT NetLogo Features O X Fully programmable Language is Logo dialect extended to support agents and parallelism Interface builder w buttons sliders monitors switches text boxes Info area for annotating your model Agent Monitors for inspecting agents Export and import model function save and restore state of model Cross platform runs on MacOS Windows Linux et al X Web enabled run within a web browser or download and run locally OX OX X__ Powerful and flexible plotting smsen N i OX EX X X X X X X X X X What is NetLogo 1 NetLogo 1 1 User Manual Models can be saved as applets to be embedded in a web page Unlimited numbers of agents and variables Double precision arithmetic Simplified language structure b o e p qr X LE X _ Agentsets make many programming tasks easier ET EE ae i a E AA
58. can explore the data from all the runs and determine how well each exhibited the behavior you are investigating The idea behind BehaviorSpace is that the way to truly understand a model is to run it multiple times with different parameter slider settings in order to see the whole range of behaviors the system is capable of producing Only then is it possible to investigate when and why certain behaviors arise Isolated trials are insufficient for this purpose because you have no reason to assume that the model will always demonstrate the particular behaviors you see It s like eating in one restaurant in New York and then claiming you ve seen all that the city has to offer By enabling you to explore the entire parameter space of a model and thus its entire space of behaviors BehaviorSpace Guide 79 NetLogo 1 1 User Manual BehaviorSpace can be a powerful tool for model understanding How It Works You begin using BehaviorSpace by setting up an experiment Its purpose is to run the model many times and collect data to determine which run best exhibits the behavior you are after In the case of Fireflies as mentioned above data might be collected to reveal how quickly synchronization happened in each run Setting up an experiment initially entails specifying in the slider values dialog what possible values each slider in the model should take in the experiment either in the form of a range or an arbitrary list which is then displayed in t
59. ce frogs mice own cheese to setup ca create custom mice 50 set color white set cheese random 10 create custom frogs 50 set color green end Programming Guide 64 NetLogo 1 1 User Manual Code Example Breeds and Shapes Example Synchronization In both StarLogoT and NetLogo turtle commands are executed asynchronously each turtle does its list of commands as fast as it can In StarLogoT one could make the turtles line up by putting ina comma At that point the turtles would wait until all were finished before any went on The equivalent in NetLogo is to come to the end of an ask block If you write it this way the two steps are not synced ask turtles fd random 10 do calculation But if you write it this way they are ask turtles fd random 10 ask turtles do calculation This latter form is equivalent to this use of the comma in StarLogoT fd random 10 do calculation Procedures advanced Here are some more advanced features you can take advantage of when defining your own procedures Procedures with inputs Your own procedures can take inputs just like primitives do To create a procedure that accepts inputs include a list of input names in square brackets after the procedure name For example to draw polygon num sides size pd repeat num sides fd size rt 360 num sides end Elsewhere in the program you could ask turtles to each draw an octagon with a sid
60. ch model runs as they progress but it may be helpful to monitor the progress of the experiment The dialog can be exited safely by hitting the cancel button This will abort the experiment If the experiment is allowed to run to completion then this dialog disappears and is replaced by the Evaluation Window Component descriptions Graphics window Displays the state of the current model run e Has a fixed size and does not allow for more than 300 patches across in either direction e Is completely equivalent to the graphics window in the main interface in all other respects Graphics on checkbox When unselected graphics are temporarily turned off although the model proceeds normally e Turning graphics off can make your experiment run significantly faster e Can be selected and unselected repeatedly during an experiment Current run number slider values time click text Displays the number of the current run being performed the values of the sliders in that run and the number of time clicks that have elapsed Behavior plot Plots the value of the behavior reporter as the model run progresses Cancel button Aborts the experiment at which point the progress dialog quits Evaluation Window The evaluation window is perhaps the most complex part of BehaviorSpace but also the most flexible and powerful It is designed to allow you to visually explore the behavior data reported by the model runs It works by holding the values of al
61. choice and user input for accepting input from user new primitive read f rom string for converting strings e g user input or input from a file into data What s New 4 NetLogo 1 1 User Manual the and and or primitives now short circuit which means they no longer evaluate their right hand arguments unless necessary message primitive renamed to user message e engine fixes fixed Windows only bug where models that used p1ot pen reset a lot tended to crash NetLogo the random primitive now works properly on negative integers and on zero fixed bug in cct hatch and sprout where sometimes the new turtle was not initialized immediately fixed bug where setting a turtle s x or y coordinate to an extremely large value could cause NetLogo to stop responding fixed bug where editing screen edge x y didn t empty the breed agentsets the turtle and patch primitives now signal a runtime error if passed non integer arguments fixed compiler bug that could cause a confusing error message if you used an observer only primitive in the same context as a turtle patch only primitive fixed bug where sometimes patches containing only hidden turtles were drawn with an incorrect color fixed bug where changing a label s color didn t always redraw the whole label immediately using the double quote character in a plot pen name no longer confuses NetLogo fixed rare bug where a runtime error could cause Java exceptions if it occurred inside
62. culator lists such as L1 or PLOTS 0 Valid calculator matrices such as A or B 0 Valid calculator strings such as Str1 or Str5 0 Numbers such as A or B This primitive must be called before you try to check for data on the server using the hubnet message waiting reporter hubnet set client interface client type activity name If client type is Tl 83 notify the user to enable the activity activity name on the TI Navigator web site Future versions of HubNet may support other client types and or change the meaning of the second input to this command These are usually best called from the st artup procedure of the NetLogo model Data extraction The data extraction primitives are hubnet message waiting This looks for new information on the server It returns TRUE if there is new data and FALSE if there is not hubnet fetch message This retrieves any new data from the server so that it can be accessed by hubnet message This will cause an error if no data is on the server So be sure to check HubNet Guide 74 NetLogo 1 1 User Manual for data with hubnet message waiting before calling this hubnet message source This reports the user ID that sent the data This will cause an error if no data has been fetched from the server So be sure to fetch the data with hubnet fetch message before calling this hubnet message tag This reports the variable name that was sent This will only report one of the tags set with the h
63. d about it by going to the Primitives Dictionary and it may help to toy with the values being passed to it and see what happens We re now prepared to create some kind of dialog between the turtles and the patches In fact we even have an idea for a project here Notice that we called the patch variable elevation and that our landscape sort of looks topographical We re going to have our turtles do what is called hill climbing where every turtle seeks to find the highest elevation it can We ll now explain the notion of compound commands a feature that makes NetLogo quite different from StarLogoT and somewhat closer to natural language Go to the Command Center and type O gt show max values from patches elevation and show min values from patches elevation These two reporters will respectively search over all the patches to return to you the highest elevation and the lowest These commands work like this you can read about them in the NetLogo Dictionary too Look up values from in the dictionary It shows values from AGENTSET expression and says it returns a list In this case it looks at the expression elevation for each agent in the agentset patches and returns all of these as a list of elevations Look up min in the dictionary It shows min is and says it s a reporter So it takes the list of elevations and reports the smallest value Show displays this value in the command center And there you have
64. d setup and a forever button that calls a procedure called Programming Guide 58 NetLogo 1 1 User Manual go In NetLogo you must specify which agents turtles patches or the observer are to run each command If you don t specify the code is run by the observer In the code above the observer uses ask to make the set of all turtles run the commands between the square brackets ca and crt can only be run by the observer d on the other hand can only be run by turtles Some other commands and reporters such as set can be run by different agent types Variables Variables are places to store values such as numbers A variable can be a global variable a turtle variable or a patch variable If a variable is a global variable there is only one value for the variable and every agent can access it But each turtle has its own value for every turtle variable and each patch has its own value for every patch variable Some variables are built into NetLogo For example all turtles have a color variable and all patches have a pcolor variable The patch variable begins with p so you won t get it confused with the turtle variable If you set the variable the turtle or patch changes color See next section for details Other predefined turtle variables including xcor ycor and heading Other predefined patch variables include pxcor and pycor There is a complete list here You can also define your own variables
65. d thereby determine fitness can be based on simple point statistics such as maximum or mean value or by slope which is sensitive to the data s behavior not to be confused with the model s behavior over time In addition to changing the values of the constant sliders and alternating which sliders get to be on the axes of the landscape these two operations let you explore the model s parameter space you can see the data from each run represented on the landscape plotted on a behavior plot by moving your mouse over that run s corresponding square You can learn more about how evaluation of the experimental data works in the evaluation window part of the Interface Reference section below Interface Reference This section describes the interface to BehaviorSpace Included is a general description of each of the three main BehaviorSpace windows a list of the interface components they contain as well as a description of those components It is intended mainly as a reference The windows are discussed in the order you use them first the Setup Window then the Progress Dialog and finally the Evaluation Window Setup Window This is the window in which you set up an experiment Setting up an experiment requires entering information in the fields outlined below then pushing the run comparison button When opening and closing models or changing the existing model the setup window is automatically updated so there is no need to close and
66. e show show value Prints value in the Command Center preceded by the calling agent and followed by a carriage return The calling agent is included to help you keep track of what agents are producing which lines of output See also_print type showturtle st showturtle The turtle becomes visible again Note This command is equivalent to setting the turtle variable hidden to false See also_hideturtle sin sin number Reports the sine of the given angle Assumes angle is given in degrees show sin 270 gt 1 0 Primitives Dictionary 137 NetLogo 1 1 User Manual sort sort list Reports a new list containing the same elements as the input list but in ascending order If there is at least one number in the list the list is sorted in numerically ascending order and any non numeric elements of the input list are discarded If there are no numbers but at least one string in the list the list is sorted in alphabetically ascending order and any non string elements are discarded sprout sprout number commands EI Creates number new turtles on the current patch The new turtles have random colors and orientations and they immediately run commands This is useful for giving the new turtles different colors headings breeds or whatever sprout 1 set color red Note While the commands are running no other agents are allowed to run any code as with the without interruption command This ensures t
67. e center of the world has coordinates 0 0 We call the patch s coordinates pxcor and pycor Just like in the standard mathematical coordinate plane pxcor increases as you move to the right and pycor increases as you move up The total number of patches is determined by the settings screen edge x and screen edge y When NetLogo starts up both screen edge x and screen edge y are 17 This means that pxcor and pycor both range from 17 to 17 so there are 35 times 35 or 1225 patches total You can change the number of patches by editing NetLogo s Graphics window Turtles have coordinates too xcor and ycor A patch s coordinates are always integers but a turtle s coordinates can have decimals For speed NetLogo always draws a turtle on screen as if it were standing in the center of its patch but in fact the turtle can be positioned at any point within Programming Guide 57 NetLogo 1 1 User Manual the patch The world of patches isn t bounded but wraps so when a turtle moves past the edge of the world it disappears and reappears on the opposite edge Every patch has the same number of neighbor patches if you re a patch on the edge of the world some of your neighbors are on the opposite edge Procedures In NetLogo commands and reporters tell agents what to do Commands are actions for the agents to carry out Reporters carry out some operation and report a result either to a command or another reporter Comma
68. e if any turtles have moved to go set turtles moved false move to local max do plots if not turtles moved stop end e n move to local max if a turtle moves set turtles moved to true to move to local max ask turtles set heading uphill elevation if elevation of patch at dx dy elevation ide MOM set turtles moved tru end Finally what rules can you think of that would help turtles escape from lower peaks and all get to the highest ones Try writing them What s Next So now you have a nice framework for exploring this problem of hill climbing using all sorts of NetLogo modeling features buttons sliders monitors plots and the graphics window You ve even written a quick and dirty procedure to give the turtles something to do And that s where this tutorial leaves off You can continue with this model if you d like experimenting with different variables and algorithms to see what works the best what makes the most turtles reach the peaks Alternatively you can look at other models or go ahead and build you own You don t even have to model anything It can be pleasant just to watch patches and turtles forming patterns or whatever Hopefully you will have learned a few things both in terms of syntax and general methodology for model building The entire code as created above is shown below Appendix Complete Code The complete model is also available in NetLogo s Models Library in t
69. e length equal to its ID number ask turtles draw polygon 8 who Reporter procedures Just like you can define your own commands you can define your own reporters You must do two special things First use to report instead of to to begin your procedure Then in the body of the procedure use report to report the value you want to report Programming Guide 65 NetLogo 1 1 User Manual to report absolute value number ifelse number gt 0 report number report 0 number end Procedures with local variables A local variables is defined and used only in the context of a particular procedure To add a local variable to your procedure use the locals keyword It must come at the beginning of your procedure For example to swap colors turtlel turtle2 locals temp set temp color of turtlel set color of turtlel color of turtle2 set color of turtle2 temp end Lists In the simplest models each variable holds only one piece of information usually a number or a string The list feature lets you store multiple pieces of information in a single variable by collecting those pieces of information in a list Each value in the list can be any type of value a number or a string an agent or agentset or even another list Lists allow for the convenient packaging of information in NetLogo If your agents carry out a repetitive calculation on multiple variables it might be easier to have a list variable instead
70. e size the same size as all the patches The Turtle Sizes checkbox lets you turn on an optional feature where turtles can be drawn in all different sizes The size of each turtle is controlled by its size turtle variable In most NetLogo models every turtle is always drawn as if it were standing on the center of its patch The Exact Turtle Positions checkbox lets you turn on an optional feature where turtles can be drawn in their exact positions within a patch Note the Turtle Sizes and Exact Turtle Positions features may make your model run a lot slower and or cause display anomalies We plan to improve these features in a future version of NetLogo Command Center The Command Center allows you to issue commands directly without adding them to the model s procedures Commands are instructions you give to turtles patches and the observer This is useful for inspecting and manipulating agents on the fly Tutorial 2 Commands is an introduction to using commands in the Command Center Let s take a closer look at the design of the Command Center Command Center Clear T set color red P set pcolor white O ask turtle 10 set color blue O ask turtle 1 set color blue 9s crt 10 14 You will notice there is a large display box an agent popup menu O gt a clear button and the history popup menu with the little black triangle The top large display box temporarily stores all of Interface Guide
71. e the Export Plot item on the File menu It saves this information to your computer in a format that can by read back by spreadsheet and database programs such as Excel Monitors Monitors are another method of displaying information in a model Here are the monitors in Wolf Sheep Predation e ticks sheep wolves grass 4 The monitor labeled ticks tells us how much time has passed in the model The other monitors show us the population of sheep and wolves and the amount of grass Remember the amount of grass is divided by four to keep the graph from getting too tall The numbers displayed in the monitors update continuously as the model runs whereas the plots show you data from the whole course of the model run Note that NetLogo has also another kind of monitor called agent monitors These will be introduced in Tutorial 2 Changing Graphics Window Settings Changing the settings in the Graphics Window allows you to make the NetLogo world bigger or smaller The size of the Graphics Window is determined by three separate settings Screen Edge X Screen Edge Y and Patch Size Let s take a look at what happens when we change the size of the Graphics Window in the Wolf Sheep Predation model e Place your mouse pointer next to but still outside of the Graphics Window You will notice that the pointer turns into a crosshair e Hold down the mouse button and drag the crosshair over the Graphics Window T
72. e y Switching tabs or pressing the Compile button in the toolbar causes your code to be checked for errors Interface Guide 56 Programming Guide The following material explains some important features of programming in NetLogo Note If you are already familiar with StarLogo or StarLogoT then the material in the first four sections may already be familiar to you The Code Example models mentioned throughout can be found in the Code Examples section of the Models Library e Agents e Procedures e Variables e Colors e Ask e Agentsets e Breeds e Synchronization e Procedures advanced e Lists e Strings e Turtle Shapes Agents The NetLogo world is made up of agents Agents are beings that can follow instructions Each agent can carry out its own activity all simultaneously In NetLogo there are three types of agents turtles patches and the observer Turtles are agents that move around in the world The world is two dimensional and is divided up into a grid of patches Each patch is a square piece of ground over which turtles can move The observer doesn t have a location you can imagine it as looking out over the world of turtles and patches When NetLogo starts up there are no turtles yet The observer can make new turtles Patches can make new turtles too Patches can t move but otherwise they re just as alive as turtles and the observer are Patches have coordinates The patch in th
73. eading uphill elevation if elevation of patch at dx dy elevation fd 1 set turtles moved tru Tutorial 43 Procedures 47 NetLogo 1 1 User Manual end to do plots set current plot Turtles at Peaks plot count turtles with elevation gt highest 100 end Tutorial 43 Procedures 48 Interface Guide This section of the manual walks you through every element of the NetLogo interface in order and explains its function In NetLogo you have the choice of or viewing models found in the Models Library adding to existing models or creating your own models The NetLogo interface was designed to meet all these needs The interface can be divided into two main parts NetLogo menus and the main NetLogo window The main window is divided into tabs e Menus e Main Window Interface Tab 9 Interface Toolbar 0 Working With Interface Elements 0 Graphics Window amp Command Center Procedures Tab Information Tab Errors Tab Menus On Macs if you are running the NetLogo application the menubar is located at the top of the screen On other platforms and in the applet the menubar is found at the top of the NetLogo window File Edit Tools Zoom Tabs Help NetLogo new model The functions available from the menus in the menubar are listed in the following chart Chart NetLogo Menus New Era a new model Open Opens any NetLogo or StarLogoT model on your computer Models Libra
74. ed each turtle turns the patch on its left red one of one of agentset If given a turtle agentset reports the turtle in the set with the lowest numbered ID If given a patch agentset reports the patch in the set with the highest pycor and if a tie breaker is needed with the lowest pxcor If the agentset is empty reports nobody See also random one of or boolean or boolean2 Reports true if either boolean or boolean2 or both is true Note that if condition is true then condition2 will not be run since it can t affect the result if pxcor gt 0 or pycor gt 0 set pcolor red 7 patches turn red except in lower left quadrant other turtles here other BREED here other turtles here other BREED here x Reports an agentset consisting of all turtles on the calling turtle s patch not including the caller itself If a breed is specified only turtles with the given breed are included Suppose I am one of 10 turtles on the same patch show count other turtles her Primitives Dictionary 124 NetLogo 1 1 User Manual gt 9 Example using breeds breeds cats dogs show count other dogs here prints the number of dogs that are not me on my patch See also turtles here P patch patch pxcor pycor Given two integers reports the single patch with the given pxcor and pycor The coordinates are the actual coordinates they are not computed relative to the calling agent as with patch at
75. ed to have the show energy switch turned on Once you are done exploring the Wolf Sheep Predation model you may want to take some time just to explore some of the other models available in the Models Library The Models Library The library contains four sections Sample Models Code Examples HubNet Unverified Models Sample Models The Sample Models section is organized by subject area and currently contains more than 60 models We are continuously working on adding new models to it so come visit this section at a later date to view the new additions to the library Code Examples These are simple demonstrations of particular features of NetLogo They ll be useful to you later when you re extending existing models or building new ones For example if you wanted to put a histogram within your model you d look at Histogram Example to find out how HubNet Activities This section contains participatory simulations for use in the classroom For more information about HubNet see the HubNet Guide Tutorial 1 Models 24 NetLogo 1 1 User Manual Unverified Models These models are still in the process of being tested and reviewed for content and accuracy They are complete and functional we just haven t tested them as thoroughly or made sure the code is good sample code What s Next If you want to learn how to explore models at a deeper level Tutorial 2 Commands will introduce you to the NetLogo modeling language
76. eed to start refining the model Part of the problem is that our terrain is terribly lumpy Every patch picked a random elevation and then we diffused these values one time This really doesn t give us a continuous spread of elevation across the graphics window as you might have noticed We can correct this problem to an arbitrary Tutorial 3 Procedures 42 NetLogo 1 1 User Manual degree by diffusing more often Replace the line diffuse elevation 1 with repeat 5 diffuse elevation 1 The repeat primitive is another way for NetLogo to loop besides the forever button Repeat takes a number here 5 and a command list here the diffuse command and executes the command list that number of times here five times Try it out and look at the landscape i e press setup and see what you think Then press go and watch the turtles performance Remember that the lighter the patch the greater the elevation Obviously fewer peaks make for an improvement in the turtles performance On the other hand maybe you feel like this is cheating the turtles really aren t doing any better it s just that their problem was made easier True enough If you call repeat with an even higher number 40 or so you ll end up with only a handful of peaks as the values become more evenly distributed with every successive call Watch your monitor values In order to specify how smooth you want your world to be let s make it easier
77. element first To learn more about the different kinds of interface elements refer to the chart below Chart Interface Toolbar Icon Name Description gt Z gt S y O po E can be either once only buttons or forever buttons When you click on a Button once button it executes its instructions once The forever button executes the instructions over and over until you click on the button again to stop the action Slider Sliders are global variables which are accessible by all agents They are used in Slider models as a quick way to change a variable without having to recode the procedure every time Instead the user moves the slider to a value and observe hat happens in the model Op Switch Switches are a visual representation for a true false variable The user is asked to Switch set the variable to either on true or off false by adjusting the switch Monitor Monitors display the value of any expression The expression could be a variable Monitor a complex expression or a call to a reporter Monitors automatically update several times per second ad Plot Plots are real time graphs of data the model is generating Plot Did bie Text Box lets you create text labels in the Interface Tab Text Graphics Window The Graphics Window initially appears as a large black square on the Interface Tab This is the graphical world of NetLogo s turtles and patches Some NetLogo models let you interact with the turtles and p
78. em with the download form or provide an alternate method of downloading the software Downloading NetLogo takes too long Can get it some other way like on a CD At present no If this is a problem for you contact us at feedback ccl northwestern edu FAQ Frequently Asked Questions 89 NetLogo 1 1 User Manual downloaded and installed NetLogo but the Models Library has few or no models in it What s going on So far users reporting this problem all used the without VM download option for Windows Uninstall NetLogo and try the with VM download instead Even if that fixes it please contact us at bugs 2ccl northwestern edu We d like to fix this in a future version but to troubleshoot it we need help from users Usage How do change how many patches there are Select the Graphics Window by dragging a rectangle around it with the mouse Click the Edit button in the Toolbar and type in new values for Screen Edge X and Screen Edge Y You can also right click Windows or control click Mac on the Graphics Window to edit it or select it then double click How big can my model be How many turtles patches procedures buttons etc NetLogo has no fixed limits on size By default though on non Macintosh operating systems NetLogo ships with a 512 megabyte ceiling on how much total RAM your model can use But you can raise that limit by editing this section of the NetLogo lax file in the NetLogo folder
79. ent the two selected sliders Each square in the landscape then represents the particular run whose slider values are determined by the location of the square along the two axis and the current values of the sliders held constant Example Suppose you are performing an experiment with the Fireflies model that tried many possible combinations of slider values Then you select flash length and number flashes as the sliders to represent the axes of the landscape with number held constant at 1500 and cycle length at 100 Assuming flash length is on the horizontal axis and number flashes is on the vertical axis the landscape would be 10 by 3 since flash length goes from 1 to 10 and number flashes from 1 to 3 Each square on the landscape would be colored a particular shade of blue ranging from BehaviorSpace Guide 80 NetLogo 1 1 User Manual solid blue to black depending on how good i e fit the behavior of the run represented by that square was according to criteria you select For instance squares representing runs of Fireflies in which the agents synchronized their lights quickly would be more blue than those representing runs where the fireflies synchronized slowly or not at all The reason the grid is called the fitness landscape is because it displays a 2 dimensional landscape of squares each with a fitness allowing you to take in with a glance regions of high and low fitness The criteria with which you rank run data an
80. entset concept is that you can construct agentsets that contain only some turtles or some patches For example all the red turtles or the patches with pxcor evenly divisible by five or the turtles in the first quadrant that are on a green patch These agentsets can then be used by ask or by various reporters that take agentsets as inputs Programming Guide 62 NetLogo 1 1 User Manual One way is to use turtles here or turtles at to make an agentset containing only the turtles on my patch or only the turtles on some other particular patch Here are some more examples of how to make agentsets all red turtles turtles with color red all red turtles on my patch turtles here with color red patches on right side of screen patches with pxcor 0 all turtles less than 3 patches away turtles in radius 3 the four patches to the east north west and south patches at points 1 0 0 1 1 0 0 1 Shorthand for those four patches neighbors4 turtles in the first quadrant that are on a green patch turtles with xcor gt 0 and ycor gt 0 and pcolor green Once you have created an agentset here are some simple things you can do Use ask to make the agents in the agentset do something Use any to see if the agentset is empty Use count to find out exactly how many agents are in the set And here are some more complex things you can do e Pick a random agent from the set using random one o
81. er of sliders and in which every point is a particular combination of values Running a model with different slider values and sometimes even the same ones can lead to drastically different behavior in the system being modeled So how are you to know which particular configuration of values or types of configurations will yield the kind of behavior you are interested in This amounts to the question of where in its huge multi dimension parameter space does your model perform best Suppose you want speedy synchronization from the agents in the Fireflies model The model has four sliders number cycle length flash length and number flashes that have approximately 2000 100 10 and 3 possible values respectively That means there are 2000 100 10 3 600 000 possible combinations of slider values Trying combinations one at a time is hardly an efficient way to learn which one will evoke the speediest synchronization BehaviorSpace offers you a much better way to solve this problem If you specify a subset of values from the ranges of each slider it will run the model with each possible combination of those values and during each model run record the results In doing so it samples the model s parameter space not exhaustively but enough so that you will be able to see relationships form between different sliders and the behavior of the system Once all the runs are over you are presented with a visual display with which you
82. er of sliders in your model existing windows will remain unchanged Component descriptions Point statistic checkbox When this is selected the data obtained from each run will be ranked according to the items selected by the following two menus All three slope menus are made irrelevant In general it means that the data will be judged based on a simple global statistic instead of how it varies over time Point statistic type menu Determines whether run data should be ranked according to their minimum maximum mean or last value or by the number of time clicks they lasted for The latter option is only relevant when an exit condition was entered to stop runs otherwise they will all finish in the same number of time clicks Point statistic value menu Determines whether it is better for the statistic selected in the point statistic type menu to be high low or near 0 e Low means more negative so 100 is lower than 1 e Near 0 means as close to 0 as possible irrespective of sign so 5 is nearer to O than 1 Slope checkbox When selected the data from each run will be ranked according to how it behaves over time as specified by the following three menus The items selected by the previous two menus are then irrelevant Slope type menu Controls whether the run data is fit to a line or exponential curve This distinction is only relevant with regards to error since the slope of the data always remains the same The higher t
83. er the Help link HubNet Guide 73 NetLogo 1 1 User Manual Saving The data sent by calculators or NetLogo is saved in the order that the server receives the data NetLogo Commands In the model the modeler uses a set of commands to extract the data from the server The modeler is free to interpret these numbers as anything they wish A 5 could mean to set a particular patch s color to red or have a turtle move forward Setup In order for NetLogo to communicate with the server it is necessary for NetLogo to establish a connection with the server and for NetLogo to tell the server what variables to send to NetLogo This is done with the following three primitives hubnet reset This logs you into the HubNet system You must be logged in to use any of the other HubNet primitives If this is the first time called for this NetLogo session a HubNet properties dialog appears prompting you to input the appropriate information to be able to log into the HubNet system Once you press the Login button NetLogo will attempt to log you into HubNet Once you are logged in you are always logged in while this model is open you log off when you close the model or quit NetLogo hubnet set tags variable list This sets which variables NetLogo expects from the calculators NetLogo will only check for these variables and will ignore all others Currently the valid types that NetLogo will be able to receive from the calculator are the following 0 Valid cal
84. ersion of StarLogo was developed at the MIT Media Lab in 1989 90 This original version ran on a massively parallel supercomputer called The Connection Machine A few years later 1994 a simulated parallel version was developed for the Macintosh computer That version eventually became MacStarLogo The StarLogoT 1997 software developed at the Center for Connected Learning and Computer Based Modeling CCL is essentially an extended version of MacStarLogo with many additional features and capabilities Since then two multi platform Java based multi agent Logos have been developed NetLogo from the CCL and a Java based version of StarLogo from MIT The NetLogo language and environment differ in many respects from MIT StarLogo s Both languages were inspired by the original StarLogo but were redesigned in different ways NetLogo s design was driven by the need to revise and expand the language so it is easier to use and more powerful and by the need to support the HubNet architecture NetLogo also incorporates almost all of the extended functionality of our earlier StarLogoT See below for information on how to convert a StarLogoT model to NetLogo The What is NetLogo section of this manual lists some of the other features that are new in NetLogo Downloading The download form doesn t work for me Can I have a direct link to the software Please write us at bugsccl northwestern edu and we ll work with you to either fix the probl
85. erved at work may be the party starter with friends The patterns may also depend on what kind of gathering it is In some settings people are trained to organize themselves into mixed groups for example party games or school like activities But in a non structured atmosphere people tend to group in a more random manner Is there any type of pattern to this kind of grouping Let s take a closer look at this question by using the computer to model human behavior at a party NetLogo s Party model looks specifically at the question of grouping by gender at parties why do groups tend to form that are mostly men or mostly women Let s use NetLogo to explore this question What to do 1 Start NetLogo 2 Choose Models Library from the File menu Sample Model Party 13 NetLogo 1 1 User Manual wit Edit Tools Zoom Models Library 38M Save aes Save As Save As Applet Print 3P Export World Export Plot Export Output Import World Quit 36Q 3 Open the Social Science folder 4 Click on the model called Party 5 Press the open button 6 Wait for the model to finish loading 7 optional Make the NetLogo window bigger so you can see everything 8 Press the setup button In the Graphics Window you will see pink and blue lines with numbers 10 15 13 12 18 14 15 18 17 These lines represent mingling groups at a party Men are represented in blue wome
86. es Dictionary 99 NetLogo 1 1 User Manual 1 both take one unit of time but bk 3 takes three See also forward jump breeds breeds breed1 breed2 This keyword like the globals turtles own and patches own keywords can only be used at the beginning of a program before any function definitions It defines breeds and their associated agentsets Any turtle of the given breed e is part of the agentset named by the breed name e has its breed built in variable set to that agentset Most often the agentset is used in conjunction with ask to give commands to only the turtles of a particular breed breeds mice frogs to setup ca create mice 50 ask mice set color white create frogs 50 ask frogs set color green show breed of one of mic 77 prints mice show breed of one of frogs 7 prints frogs end See also globals patches own turtles own lt BREED gt own create BREED create custom BREED lt BREED gt at BREED here but first bf but last bl but first list but first string but last list but last string When used on a list but first reports all of the list items of ist except the first and but last reports all of the list items of ist except the last On strings but first and but last report a shorter string omitting the first or last character of the original string mylist is 2 4 6 5 8 12 Primitives Dictionary 100 NetLogo 1 1 User Manual set mylist but first
87. esets the current plot pen then draws a histogram of the values in the given list See histogram above for more information home home x Returns turtle to the origin Equivalent to setxy 0 0 Primitives Dictionary 112 NetLogo 1 1 User Manual hsb hsb hue saturation brightness Reports a number in the range 0 to 140 not including 140 itself that represents the given color specified in the HSB spectrum in NetLogo s color space All three values should be in the range 0 0 to 1 0 The color reported may be only an approximation since the NetLogo color space does not include all possible colors It contains only certain discrete hues and for each hue either saturation or brightness may vary but not both at least one of the two is always 1 0 show hsb 0 0 0 gt 0 black show hsb 0 5 1 0 1 0 gt 85 cyan See also extract hsb rgb extract rgb hubnet broadcast hubnet broadcast variable name value This broadcasts value from NetLogo to the variable variable name on the teacher calculator You may send a number a string a list of numbers or a matrix a list of lists of numbers See the HubNet Programming Guide for details and instructions hubnet fetch message hubnet fetch message This retrieves a new message from the server if there is one to be retrieved See the HubNet Programming Guide for details hubnet message hubnet message Reports the message retrieved by hubnet fetch messa
88. f For example we can make a randomly chosen turtle turn green set color of random one of turtles green Or tell a randomly chosen patch to sprout a new turtle ask random one of patches sprout 1 e Use the max one of Or min one of reporters to find out which agent is the most or least along some scale For example to remove the richest turtle you could say ask max one of turtles sum assets die e Make a histogram of the agentset using the histogram command e Use values from to make a list of values one for each agent in the agentset Then use one of NetLogo s list primitives to do something with the list See the Lists section below For example to find out how rich the richest turtle is you could say show max values from turtles sum assets This only scratches the surface see the Models Library for many more examples and consult the Primitives Guide and Primitives Dictionary for more information about all of the agentset primitives More examples of using agentsets are provided in the individual entries for these primitives in the NetLogo Dictionary In developing familiarity with programming in NetLogo it is important to begin Programming Guide 63 NetLogo 1 1 User Manual to think of compound commands in terms of how each element passes information to the next one Agentsets are an important part of this conceptual scheme and provide the NetLogo developer with a lot of power and flexibility as wel
89. f number is floating point has a decimal point reports a floating point number show random 3 73 prints 0 1 or 2 show random 5 0 prints a number at least 0 0 but less than 5 0 for example 4 686596634174661 random one of random one of agentset Reports a random agent chosen from the agentset If the agentset is empty reports nobody ask random one of patches set pcolor green a random patch turns green set pcolor of random one of patches green another way to say the same thing ask patches with any turtles here show random one of turtles here for each patch containing turtles prints one of those turtles See also one of random seed random seed number Sets the seed of the pseudo random number generator to the integer part of number The exact value of the seed does not matter except as indicated below If the pseudo random number generator is initialized to a fixed seed then it will generate exactly the same random sequence every time a model is run On the other hand setting the seed to different values in each run will make the sequences different for each run Primitives Dictionary 129 NetLogo 1 1 User Manual When this command is not used the pseudo random number generator uses a seed based on the current time random seed 47823 show random 100 gt 57 show random 100 gt 91 andom seed 47823 how random 100 25 show random 100 gt 91 oO K read
90. fferent world topology bounded infinite plane sphere etc Torus is the only topology directly supported by NetLogo but you can often simulate a different topology without too much extra effort If you want the world to be a bounded rectangle you may need to add some code to your model to enforce this Often a helpful technique is to turn the edge patches a different color so turtles can easily detect when they hit the edge Also there are no wrap versions of the distance and towards primitives these should help If you want your turtles to move over an infinite plane you can simulate this by having the turtles keep track of their position on the infinite plane then hide the turtle when it goes out of bounds The Random Walk 360 model in the Models Library shows you how to code this Simulating a spherical or other topology might be difficult we haven t seen a model that does this If you have one please send it in Does NetLogo have a command like StarLogo s grab command We don t have such a primitive although we plan to add one or perhaps several In the meantime though you can use the without interruption primitive new in NetLogo 1 1 to arrange exclusive interaction between agents For example turtles own mate to setup ask turtles set mate nobody end to find mate turtle procedure locals candidate without interruption if mate nobody set candidate random one of other t
91. from string read from string string Interprets the given string as if it had been typed in the Command Center and reports the resulting value The result may be a number list string or boolean value or the special value nobody Useful in conjunction with the user input primitive for converting the user s input into usable form show read from string 3 read from string 5 gt 8 show length read from string 1 2 3 gt 3 crt read from string user input Make how many turtles the number of turtles input by the user are created remove remove item list For a list reports a copy of ist with all instances of item removed For strings reports a copy of string2 with all the appearances of string as a substring removed set mylist 2 7 4 7 Bob set mylist remove 7 mylist mylist is now 2 4 Bob show remove na banana gt ba remove duplicates remove duplicates list Reports a copy of ist with all duplicate items removed The first of each item remains in place set mylist 2 7 4 7 Bob 7 set mylist remove duplicates mylist mylist is now 2 7 4 Bob Primitives Dictionary 130 NetLogo 1 1 User Manual repeat repeat number commands Runs commands number times pd repeat 36 fd 1 rt 10 the turtle draws a circle replace item replace item index list value replace item index string1 string2 On a list replaces an item in that list index is the index of
92. g is inverted If number is less than rangeft then the darkest shade of color is chosen If number is greater than range2 then the lightest shade of color is chosen Note for color shade is irrelevant e g green and green 2 are equivalent and the same spectrum of colors will be used ask turtles set color scale color red age 0 50 7 colors each turtle a shade of red proportional to its value for the age variable screen edge x screen edge y screen edge x screen edge y These reporters give the maximum x coordinate and maximum y coordinate respectively of the Graphics Window screen edge x and y are the half width and half height of the NetLogo world the distances from the origin to the edges screen size is the same as 2 screen edge 1 Note You can set the size of the Graphics Window only by editing it these are reporters which cannot be set cct 100 setxy random screen edge x random screen edge y distributes 100 turtles randomly in the first quadrant Primitives Dictionary 133 NetLogo 1 1 User Manual screen size x screen size y Screen size x Screen size y These reporters give the total width and height of the NetLogo world Screen size is the same as 2 screen edge 1 semicolon comments After a semicolon the rest of the line is ignored This is useful for adding comments to your code text that explains the code to human readers Extr
93. ge See the HubNet Programming Guide for details hubnet message source Primitives Dictionary 113 NetLogo 1 1 User Manual hubnet message source Reports the id of the device that sent the message retrieved by hubnet fetch message See the HubNet Programming Guide for details hubnet message tag hubnet message tag Reports the variable name on the device that sent the message that was retrieved by hubnet fetch message See the HubNet Programming Guide for details hubnet message waiting hubnet message waiting This looks for a new message on the server and reports true if it found one false otherwise See the HubNet Programming Guide for details hubnet reset hubnet reset Logs you into the HubNet system You must be logged in to use any of the other hubnet primitives See the HubNet Programming Guide for details hubnet set client interface hubnet set client interface client type activity name If client type is Tl 83 notify the user to enable the activity with the given name on the TI Navigator web site Future versions of HubNet may support other client types and or change the meaning of the second input to this command See the HubNet Programming Guide for details hubnet set tags hubnet set tags variable list This sets which variables NetLogo expects from the calculators NetLogo will only check for these variables and will ignore all others Primitives Dictionary 114 NetLogo 1 1 User Manual hu
94. given shape The specified breed must be either be turtles or a breed defined by the breeds keyword and the specified string must be the name of a currently defined shape In new models the default shape for all turtles is default Note that specifying a default shape does not prevent you from changing an individual turtle s shape later turtles don t have to be stuck with their breed s default shape create turtles 1 new turtle s shape is default create cats 1 new turtle s shape is default set default shape turtles circle create turtles 1 new turtle s shape is circle create cats 1 new turtle s shape is circle set default shape cats cat set default shape dogs dog create cats 1 new turtle s shape is cat ask cats set breed dogs all cats become dogs and automatically change their shape to dog set histogram num bars set histogram numc bars integer Set the current plot pen s plot interval so that given the current x range for the plot there would be integer number of bars drawn if the histogram or histogram list commands were called Primitives Dictionary 135 NetLogo 1 1 User Manual See also_histogram set plot pen color set plot pen color number Sets the color of the current plot pen to number set plot pen interval set plot pen interval number Tells the current plot pen to move a distance of number in the x direction during each use of the plot command The plo
95. go 1 1 User Manual Table of Contents Primitives Dictionary p E 126 uim EE ETT TROC T rem 127 plot pen down ppd plot pen up pop 127 PESETA osse edP inns RRA 127 Pius NOT A 127 plot x min plot x max plot y min plOt Y MDX cccoooooccccccncccnnnonnnononoccncananenonnnnnnnnnnns 127 ESSI Ree eg o UM MU d III M Hi E 128 procio ENTE A 128 A O A E 128 SE 128 ETELE eee c EIE POY E A De OE M e p EL Se eer 129 Haa SO SE estaa tka eo uo ada oi 129 RPM TES ISO EET 129 ERG gr LS MUA EEN 130 LUUD uet ru mU E LU M A DA IEEE 130 HM AE AIOE TION 130 EE m M receaeee 131 Hout m NOTTE 131 IBID us sunu A UU MAE MEL 131 A Emm 131 e E E EE I EE E S E E AAT A A E E ER 131 A E E EEI EA IA AAEE A E E E NE m 132 A E EAE nee ee te E E MR E E UM LI DI M UM d 132 elis BEE 132 BEE 133 EE ee 133 SCreen ecde vecteen eduexv tnnt tnEEtEnEEnE EEEE EEEE n EnEn EnEn 133 scr erni sizB X SCIEON SIZO Y error AA RA RARA 134 SE Ier EE a E E E E NE E E E E E 134 MA i a d a iae aiiai aaan 134 CIIM E E EEE ee 134 se cune Bob odit torte o ci BERE EBEN GR M UEM hb iG die ple helle bl ba e bla ui Deep RA 135 sel eunrent pO DO sa Ce Ent nine enero P Dru A 135 ASIS NTC EE 135 Sel T stoctam vil IS id dina 135 EENEG 136 la lo E 136 EEN cs sins tka dca DT cR 136 set plot x range set Olotv rangde 136 PP ei a nae 136 db OTT VENE ee EAN ey 137 Cue M 137
96. gy switch only changes what information is displayed but the grass switch actually makes the model behave differently Another type of setting is called a slider Sliders are a different type of setting then a switch A switch has two values on or off A slider has a range of numeric values that can be adjusted For example the initial sheep slider has a Tutorial 1 Models 19 NetLogo 1 1 User Manual minimum value of 0 and a maximum value of 250 The model could run with 0 sheep or it could run with 250 sheep or anywhere in between Try this out and see what happens As you move the marker from the minimum to the maximum value the number on the left side of the slider changes this is the number the slider is currently set to Let s investigate Wolf Sheep Predation s sliders e Read the contents of the Information tab located above the toolbar to learn what each of this models sliders represents The Information tab is extremely helpful in gaining insight into the model Within this tab you will find an explanation of the model suggestions on things to try and other information You may want to read the Information tab before running a model or you might want to just start experimenting then look at the Information tab later What would happen to the sheep population if there was more initial sheep and less initial wolves at the beginning of the simulation e Turn both of the switches off e Set the init sheep
97. h pcolor red prints the number of red patches without interruption without interruption commands The agent runs all the commands in the block without allowing other agents to interrupt That is other agents are put on hold and do not execute any commands until the commands in the block are finished Note you may not use without interruption in a context where the code is already running uninterrupted Other commands that establish such a context besides without interruption itself are hatch sprout and create custom turtles We plan to lift this restriction in a future version of NetLogo crt 5 ask turtles without interruption type 1 fd 1 type 2 1212121212 because each turtle will output 1 and move then output 2 however ask turtles type 1 fd 1 type 2 1111122222 because each turtle will output 1 and move then output 2 Primitives Dictionary 146 NetLogo 1 1 User Manual word word value value2 Concatenates the two inputs together and reports the result as a string show word tur tle gt turtle word a 6 gt a6 set directory c foo fish show word directory bar txt gt c foo fish bar txt show word 1 54 8 fishy gt 1 54 8 fishy wrap color wrap color number wrap color checks whether number is in the NetLogo color range of 0 to 140 not including 140 itself If it is not wrap color wraps the numeric input to the 0 to 140
98. hat the new turtles cannot interact with any other agents until they are fully initialized In addition no screen updates take place until the commands are done This ensures that the new turtles are never drawn on screen until they are fully initialized sqrt sqrt number Reports the square root of number stamp stamp color Sets the color of the patch under the turtle to the given color repeat 30 stamp yellow fd 3 rt 6 the turtle records its arched path contrast to the effect of pen down standard deviation Primitives Dictionary 138 NetLogo 1 1 User Manual standard deviation list Reports the unbiased statistical standard deviation of a ist of numbers Ignores other types of items show standard deviation 1 2 3 4 5 6 gt 1 8708286933869707 show standard deviation values from turtles energy prints the standard deviation of the variable energy from all the turtles startup startup User defined procedure which if it exists will be called when a model is first loaded to startup setup end stop stop The calling agent exits immediately from the enclosing procedure ask or ask like construct cct hatch sprout Only the current procedure stops not all execution for the agent Note stop can be used to stop a forever button If the forever button directly calls a procedure then when that procedure stops the button stops In a turtle or patch forever button the button won
99. he Code Examples section It s called Tutorial Example patches own elevation elevation of the patch globals highest maximum patch elevation Tutorial 3 Procedures 46 NetLogo 1 1 User Manual lowest minimum patch elevation turtles moved so we know when to stop the model We also have two slider variables number and 7 smoothness number determines the number of turtles and smoothness determines how erratic terrain becomes during diffusion of elevation resets everything to setup ca setup patches setup turtles end creates a random landscape of patch elevations to setup patches ask patches set elevation random 10000 repeat smoothness diffuse elevation 1 ask patches set pcolor scale color green elevation 1000 9000 set highest max values from patches elevation set lowest min values from patches elevation ask patches if elevation highest 100 set pcolor white if elevation lowest 100 set pcolor black end initializes the turtles to setup turtles crt number ask turtles if color green set color red fd random screen edge x end RUN TIME PROCEDURES main program control to go set turtles moved false move to local max do plots if not turtles moved stop end 7 performs a greedy search of radius 1 for highest elevation to move to local max ask turtles set h
100. he Graphics Window is now selected which you know because it is now surrounded by a gray border Tutorial 1 Models 21 NetLogo 1 1 User Manual e Press the Edit button on the Interface toolbar near the top of the NetLogo window A dialog box will open containing all the settings for the Graphics Window Editing Graphics Patch Size pixels Font Size of turtle and patch labels M Turtle Shapes O Turtle Sizes experimental J Exact Turtle Positions experimental What are the current settings for Screen Edge X Screen Edge Y and Patch Size e Press cancel to make this window go away e Select the Graphics Window again e Drag one of the square black handles at the edges and corners of the Graphics Window e Edit the Graphics Window again and look at the settings What numbers changed What numbers didn t change The NetLogo world is a two dimensional grid of patches Patches are the individual squares in the grid In Wolf Sheep Predation when the grass switch is on the individual patches are easily seen because some of them are green while others are brown Think of the patches as being like square tiles in a room with a tile floor Exactly in the middle of the room is a tile labeled 0 0 meaning that if the room was divided in half one way and then the other way these two dividing lines would intersect on this tile We now have a coordinate system that will help us locate objects with
101. he bottom right corners like this T go Once buttons don t have the arrows Once buttons do one action and then stop When the action is finished the button pops back up Note If you do not wait for the button to pop back up before pressing any other buttons the model might get confused and you may receive get an error message Most models including Wolf Sheep Predation have a once button called setup and a forever button called go Many models also have a once button called go once or step once which is like go except that it advances the model by one time step instead of continuously Using this button lets you watch the progress of the model more closely Forever buttons do an action over and over again When you want the action to stop press the button again It will finish the current action then pop back up Stopping a forever button is the normal way to stop a model It s safe to pause a model by stopping a forever button then make it go on by pressing the button again You can also stop a model with the Halt button on the Interface toolbar but you should only do this if the model is stuck for some reason The Halt button may interrupt the model in the middle of an action and as the result the model could get confused e If you like experiment with the setup and go buttons in the Wolf Sheep Predation model Adjusting Settings Sliders and Switches The settings within a model give you an opport
102. he sliders list You can also dictate how long each run should last either by entering the number of times the forever button should be called in the time clicks text box or by providing a reporter in the exit condition text area that causes the run to stop when it reports a boolean value of true Next you must specify a behavior reporter which is the data you want continually recorded during a model run For Fireflies this would be the current extent of synchronization in the model say the number of fireflies currently lit up which you could enter with the following reporter count turtles with color yellow By collecting this data repeatedly throughout a run an overall assessment can later be made as to how quickly synchronization was achieved Finally you may select a setup button to initialize the model and the forever button that continues it By inputting the above information you have told the system enough that it can run an experiment As the experiment proceeds it will produce data about each model run based on the behavior reporter you gave it In its raw form this data is dry and difficult to interpret it is just long series of numbers BehaviorSpace s job makes the data intuitively accessible by presenting it visually It does so by allowing you to hold the values of all sliders but two constant then presenting you with a grid of squares called a fitness landscape The axes of the fitness landscape repres
103. he tolerance Sample Model Party 15 NetLogo 1 1 User Manual Test your predictions on the model Can you see any other factors or variables that might affect the male to female ratio within each group Make predictions and test your ideas within this model Feel free to manipulate more than one variable at a time As you are testing your hypotheses you will notice that patterns are emerging from the data For example if you keep the number of people at the party constant but gradually increase the tolerance level more mixed groups appear How high does the tolerance value have to be before you get mixed groups What percent tolerance tends to produce what percentage of mixing Thinking With Models Using NetLogo to model situations like this party scenario allows you to experiment with a system in a rapid and flexible way that would be difficult to do in a real world situation Modeling also gives you the opportunity to observe a situation or circumstance with less prejudice as you can examine the underlying dynamics of a situation You may find that as you model more and more many of your preconceived ideas about various phenomena will be challenged For example a surprising result of the Party model is that even a little intolerance tends to produce a great deal of separation between the sexes This is a classic example of an emergent phenomenon where a group pattern results from the interaction of many individuals
104. he weight selected in the relative weight menu the less this menu selection matters because that means slope matters increasingly more than error Error is determined by attempting to fit the data to either a line or a curve depending on which is chosen and then finding the Least Square Error involved in doing so e Fitting data to a line means finding a function of the form y ax b that best approximates the data BehaviorSpace Guide 84 NetLogo 1 1 User Manual e Fitting data to an exponential curve means finding a function of the form y ae bx where e 2 71828 that best approximates the data e If exponential is selected and any run has both positive and negative data values then a warning dialog is brought up saying that the data cannot be fit to an exponential curve and linear is automatically selected this occurs because exponential curves of this form can be either above the x axis when a is positive or below the x axis when a is negative but not both Slope value menu Determines whether it is better for the data to be increasing the more positive the slope the better decreasing the more negative the better or constant the closer to 0 the better Relative weight menu Determines the relative importance of the slope of the data compared to how well it fits a line or exponential curve see slope type menu If 60 is chosen then 60 of the data s rank comes from its slope how much it is i
105. ice in the Procedures window Function Activity is a good one to start with Appendix HubNet Architecture HubNet Guide 75 HubNet Guide NetLogo 1 1 User Manual THE HUBNET ARCHITECTURE 76 Shapes Editor Guide The Shapes Editor allows you to create and save turtle designs NetLogo uses fully scalable and rotatable vector graphics which means it lets you create designs by combining basic geometric figures which can appear on screen in any size or orientation Getting Started To begin making shapes choose Shapes Editor on the Tools menu A new window will open with a list of all the shapes beginning with default and a row of action buttons including new edit copy and import Creating and Editing Shapes Press the new button and the editing window will appear The shape you make will appear in the main drawing area and in the three smaller preview areas found on the left side of the editing window The preview areas show your shape at different sizes as it might appear within your model as well as how it looks while rotating The rotation feature can be turned off if you want a shape that always stays right side up There are four shape drawing tools select from four button icons each of which can be filled with color or not and a background grid to guide you You can move and size these shapes with the mouse pointer as a drawing tool The shape created last will fall on top Layers can be removed wi
106. in a particular turtle You can can also edit the values of the turtle s variables and issue commands to the urtle You can also open a turtle monitor via the Graphics Window see the Graphics Window section below Eh apes Editor Draw turtle shapes See the Shapes Editor Guide for more information BehaviorSpace Runs the model over and over with different settings See the BehaviorSpace Guide for more information Bee pens the overall screen size of the model Useful on large monitors or hen using a projector in front of a group Normal Size Reset the screen size of the model to the normalsize Smaller Decrease the overall screen size of the model his menu offers keyboard shortcuts for each of the tabs On Macs it s PM 1 through Command 4 On Window it s Control 1 through Control A Hele NetLogo Information on the current NetLogo version the user is running On Macs ne menu item is on the Apple menu instead User Manual Opens this manual in a web browser Main Window At the top of NetLogo s main window are four tabs labeled Interface Procedure Information and Errors Only one tab at a time can be visible but you can switch between them by clicking on the tabs at the top of the window 000 NetLogo new model Interface einem 0 Ed Halt te Edit Button Slider Switch Monitor Plot Text Interface Guide 50 NetLogo 1 1 User Manual
107. in the room Tutorial 1 Models 22 NetLogo 1 1 User Manual How many tiles away is the 0 0 tile from the right side of the room How many tiles away is the 0 0 tile from the left side of the room In NetLogo the distance the middle tile is from the right or left edge of the room this is called Screen Edge X And the distance the middle tile is from the top and bottom edges is called Screen Edge Y 0 0 Screen Edge X Screen Edge X Screen Edge Y 0 0 Screen Edge Y In these diagrams Screen Edge X is 3 and Screen Edge Y is 2 When you change the patch size the number of patches tiles doesn t change the patches only get larger or smaller on the screen Tutorial 1 Models 23 NetLogo 1 1 User Manual Let s look at the effect of changing Screen Edge X and Screen Edge Y e Using the Edit dialog that is still open change Screen Edge X to 30 and Screen Edge Y value to 10 What happened to the shape of the Graphics Window e Press the setup button Now you can see the new patches you have created e Edit the Graphics Window again e Change the patch size to 20 and press OK What happened to the size of the Graphics Window Did its shape change Editing the Graphics window also lets you change two other settings the font size of labels and whether the Graphics Window uses shapes Feel free to experiment with these settings as well In order to see the effect of the font size settings you ll ne
108. ing Guide Now that we have familiarized ourselves with the Command Center let s work on our list of changes we wanted to make to Traffic Basic Working With Colors You may have noticed in the previous section that we used two different words for changing color color and pcolor What is the difference between color and pcolor e Choose Turtles from the popup menu in the Command Center or use the tab key e Type set color blue and press return What happened to the cars Think about what you did to make the cars turn blue and try to make the patches turn red If you try to ask the patches to set color red an error message occurs Command Center gt set color yellow ERROR You can t use COLOR ina patch context because OLOR is turtle only eType set pcolor red instead and press return We call color and pcolor variables Some commands and variables are specific to turtles and some are specific to patches For example the color variable is a turtle variable while the pcolor variable is a patch variable Go ahead and practice altering the colors of the turtles and patches using the set command and these two variables Tutorial 2 Commands 29 NetLogo 1 1 User Manual To be able to change patches and turtles colors or shall we say cars and backgrounds we have to gain a little insight into how NetLogo deals with colors In NetLogo all colors have a numeric value In all of the exercises we have
109. ing to execute the commands You can also use the tab key which is more convenient than using the popup menu T2 commands is identical to O gt ask turtles commands and P commands is identical to O gt ask patches commands You might try typing T gt pendown into the Command Center or changing set heading random 360 to It random 45 Or instead of saying crt 700 in setup say crt number where number is a slider variable and create a slider from the toolbar just as you created the buttons Play around It s easy and the results are immediate and visible one of NetLogo s many strengths Regardless the tutorial project continues Patches and Variables Now we ve got 100 turtles aimlessly moving around completely unaware of anything else around them Let s make things a little more interesting by giving these turtles a nice background against which to move Go back to the setup procedure We can rewrite it as follows patches own elevation Tutorial 3 Procedures 38 NetLogo 1 1 User Manual to setup ca setup patches setup turtles end to setup patches ask patches set elevation random 10000 diffuse elevation 1 ask patches set pcolor scale color green elevation 1000 9000 end to setup turtles crt 100 ask turtles d random screen edge x end The line at the top patches own elevation declares that we have a variable for the patches called elevation Our setup patches procedure then use
110. is exponentiation lt is less than gt is greater than is equal to is not equal to lt is less than or equal gt is greater than or equal All of the comparison operators also work on strings and the addition operator also functions as a string concatenation operator see example below If you are not sure how NetLogo will interpret your code you should insert parentheses show 5 6 6 3 gt 32 show 5 6 6 3 gt 20 show tur tle gt turtle ask ask agentset commands ask agent commands Takes a list of commands that will be run by the specified agent or agentset ask turtles fd 1 all turtles move forward one step ask patches set pcolor red all patches turn red ask turtle 4 rt 90 only the turtle with id 4 turns right at points agentset at points x1 y1 x2 y2 Reduces the given agentset to include only the agents on the patches the given distances away from the calling agent The distances are specified as a list of two item lists where the two items are the x and y offsets If the caller is the observer then the points are measured relative to the origin in other words the points are taken as absolute patch coordinates If the caller is a turtle the points are measured relative to the turtle s exact location and not from the center of the patch under the turtle ask turtles at points 2 4 1 2 10 15 EL Ge TL only the turtles o
111. is run after every time click The exit condition can be any valid NetLogo reporter that evaluates to true or false such as those that use the operators lt gt lt or gt Example The following exit condition causes model runs of Wolf Sheep Predation to stop after either population is extinct not any sheep or not any wolves Setup and forever button menus Allow you to select the optional setup button and mandatory BehaviorSpace Guide 82 NetLogo 1 1 User Manual forever button for an experiment The setup button if selected is called once at the beginning of a model run while the forever button is called repeatedly to run the model e To forgo the use of a setup button in an experiment select the lt none gt option in the setup button menu e If you choose the same button can be used as both the setup and forever buttons e f either the setup or forever button is chosen to be a forever button in your model then one call to it i e one time click amounts to one call to its code notto repeated calling of that code just as if the actual button had been pressed Run comparison button Begins the experiment which is based on the input to the interface elements listed above Progress Dialog This dialog appears automatically when an experiment begins to show you its progress It contains real time information about the current model run and the experiment as a whole It isn t necessary that you always wat
112. is the observer dx and dy are calculated from the origin 0 0 7 suppose I have 40 turtles at the origin show count turtles at 0 0 gt 40 If the name of a breed is substituted for turtles then only turtles of that breed are counted breeds cats dogs create custom dogs 5 setxy 2 3 show count dogs at 2 3 gt 5 turtles here BREED here turtles here BREED here Reports an agentset containing all the turtles on the caller s patch including the caller itself if it s a turtle ca crt 10 ask turtle 0 show count turtles here gt 10 If the name of a breed is substituted for turtles then only turtles of that breed are counted breeds cats dogs create cats 5 create dogs 1 ask dogs show count cats here gt 5 See also other turtles here turtles own BREED own turtles own var1 var2 BREED own var1 var2 The turtles own keyword like the globals breed lt BREED gt own and patches own keywords can only be used at the beginning of a program before any function definitions It defines the variables Primitives Dictionary 142 NetLogo 1 1 User Manual belonging to each turtle If you specify a breed instead of turtles only turtles of that breed have the listed variables More than one breed may list the same variable breeds cats dogs hamsters turtles own eyes legs applies to all breeds cats own fur kittens hamsters own fur cage dogs own hair pu
113. it We will use this compound command in our model One last thing before we return to the coding Those two values we just read the highest and the lowest elevations might be nice to know Rather than have to retype that every time let s use a shortcut First at the top of your code right after the patches own declaration declare two global variables as such globals highest the highest patch elevation lowest the lowest patch elevation and in setup patches write to setup patches ask patches set elevation random 10000 diffuse elevation 1 ask patches set pcolor scale color green elevation 1000 9000 set highest max values from patches elevation set lowest min values from patches elevation ask patches if elevation highest 100 Tutorial 3 Procedures 40 NetLogo 1 1 User Manual set pcolor white if elevation lowest 100 set pcolor black end Now we have saved the highest and lowest points in our terrain and displayed them graphically Look at the last two statements the if statements Each patch looks at both of these statements and compares its own value of elevation to our global variables highest and lowest If the comparison evaluates to true the patch executes the list of commands inside the brackets In this case it simply changes its color If the comparison evaluates to false the patch skips over the commands What this does is that all patches whose val
114. iven time Note that we use the plot primitive to add the next point to a plot but before doing that we need to tell NetLogo which plot we want since later our model might have more than one plot Thus we re plotting the number of turtles within 100 units of our maximum elevation at some given point in time The plot command moves the current plot pen to the point that has x coordinate equal to 1 greater than the old x coordinate and y coordinate equal to the value given in the plot command in this case the number of turtles with elevation gt highest 100 Then the plot command draws a line from the current position of the plot pen to the last point it was on In order for set current plot Turtles at Peaks to work you ll have to add a plot to your model in the Interface tab then edit it so its name is Turtles at Peaks the exact same name used in the code Even one extra space will throw it off it really must be exactly the same in both places Note that when you create the plot you can set the minimum and maximum values on the x and y axes and the color of the default plot pen pick any color you like You ll want to leave the Autoplot checkbox checked so that if anything you plot exceeds the minimum and maximum values for the axes the axes will automatically grow so you can see the whole plot Now reset the project and run it again You can now watch the plot be created as the model is running Tutorial 3
115. l as being more similar to natural language Code Example Ask Agentset Example Breeds NetLogo allows you to define different breeds of turtles Once you have defined breeds you can go on and make the different breeds behave differently For example you could have breeds called sheep and wolves and have the wolves try to eat the sheep You define breeds using the breeds keyword at the top of your model before any procedures breeds wolves sheep When you define a breed such as sheep an agentset for that breed is automatically created so that all of the agentset capabilities described above are immediately available with the sheep agentset The following new primitives are also automatically available once you define a breed create sheep create custom sheep cct sheep for short sheep here and sheep at Also you can use sheep own to define new turtle variables that only turtles of the given breed have A turtle s breed agentset is stored in the breed turtle variable So you can test a turtle s breed like this if breed wolves Note also that turtles can change breeds A wolf doesn t have to remain a wolf its whole life Let s change a random wolf into a sheep ask random one of wolves set breed sheep The set default shape primitive is useful for associating certain turtle shapes with certain breeds See the section on shapes below Here is a quick example of using breeds breeds mi
116. l but two sliders constant then drawing a grid of squares called a fitness landscape that represents all possible value combinations of the last two The values held BehaviorSpace Guide 83 NetLogo 1 1 User Manual constant by the former sliders can be changed and any of these sliders can be swapped in for one of the two sliders representing the axes on the grid In this way you are essentially focusing on two sliders at a time seeing what relationships exist between their values and the behavior of the model At the top of the window is a collection of radio boxes and pull down menus through which you can select criteria to rank the data reported by the different runs These criteria can be changed as often as you wish enabling you to highlight more than just one property of the data Data can be ranked by slope characteristics such as how much it increases over time or the extent to which it can be fit to an exponential curve or the data can be ranked by a point statistic such as its mean or minimum value Finally you are able to mouse over the landscape and as the mouse passes over each square which represents a single model run the data from that run is plotted on the behavior plot to the left Every time an experiment is run a new evaluation window is created so there can potentially be many on the screen at once Each however only represents the data from the experiment that created it so even if you change the name or numb
117. le 4 lf you want press Go button to continue running the model from the point where it left off If you wish to import a file from a location other than the NetLogo folder you may include the full path to the file you wish to import See export world for an example in radius agentset in radius number ist a Reports an agentset that includes only those agents from the original agentset whose distance from the caller is less than or equal to number ask turtles ask patches in radius 3 set pcolor red each turtle makes a red splotch around itself inspect inspect agent Opens an agent monitor for the given agent turtle or patch inspect patch 2 4 an agent monitor opens for that patch inspect random one of sheep an agent monitor opens for a random turtle from the sheep breed int int number Reports the integer part of number any fractional part is discarded show int 4 7 gt 4 show int 3 5 gt 3 is list is list value Reports true if value is a list false otherwise Primitives Dictionary 116 NetLogo 1 1 User Manual item item index list item index string On lists reports the value of the item in the given list with the given index On strings reports the character in the given string at the given index Note that the indices begin from 0 not 1 The first item is item 0 the second item is item 1 and so on 7 Suppose mylist is 2 4 6 8 10 show ite
118. ling more RAM should help If your hard drive makes a lot of noise while your model is running you probably need more RAM e If you are on Windows make sure you are running with the IBM 1 1 VM You can check in the About NetLogo window This is the VM that is bundled with NetLogo if you choose the With VM download option NetLogo s graphics are much faster with this VM than any other VM If you are not using the IBM 1 1 VM then the next tip will be especially helpful e Use the no display primitive to turn graphics off temporarily In many cases though if you want your model to run faster you may need to make some changes to the code Usually the most obvious opportunity for speedup is that you re doing too many computations that involve all the turtles or all the patches Often this can be reduced by reworking the model so that it does less computation per time step If you need help with this if you contact us at feedback ccl northwestern edu we may be able to help if you can send us your model or give us some idea of how it works The members of the NetLogo Users Group may be able to help as well Improving the speed of NetLogo is a very high priority for us You can expect future versions to be faster want to try HubNet Can I Currently using HubNet requires Texas Instruments calculator network system called Navigator We plan to lift this requirement in the near future In the meantime Navigator is currently only available
119. lized In addition no screen updates take place until the commands are done This ensures that the new turtles are never drawn on screen in an only partly initialized state hatch 1 1t 45 fd 1 each turtle creates one new turtle and the child turns and moves away hideturtle ht Primitives Dictionary 111 NetLogo 1 1 User Manual hideturtle The turtle makes itself invisible Note This command is equivalent to setting the turtle variable hidden to true See also showturtle histogram histogram agentset reporter Resets the current plot pen then draws a histogram of the values reported when all agents in the agentset run the given reporter It should report a numeric value Any non numeric values reported are ignored The histogram is drawn on the current plot using the current plot pen and pen color Use set plot x range to control the range of values to be histogrammed and set the pen interval either directly with set plot pen interval or indirectly via set histogram num bars to control how many bars that range is split up into Be sure that if you want the histogram drawn with bars that the current pen is in bar mode mode 1 histogram turtles color draws a histogram showing how many turtles there are Of each color Note using this primitive amounts to the same thing as writing histogram list values from agentset reporter butis more efficient histogram list histogram list list R
120. ly through the city As the simulation runs data is collected which can then be analyzed with the calculators afterwards For more information on participatory simulations and their learning potential please visit the Participatory Simulations Project web site e About HubNet What do need to get started First time NetLogo user Teacher workshops e Getting Started With HubNet How to use NetLogo About the activities Running an activity Proxy servers and firewalls e HubNet Programming Guide e Appendix HubNet Architecture About HubNet What do need to get started A computer with an attached projector This computer will run NetLogo and project the simulation for class viewing A classroom set of TI 834 graphing calculators e TI Navigator wireless calculator network NOTE Navigator is not yet commercially available To learn more about the system visit Texas Instruments site In the future we hope to support other input devices such as laptops and PDA s Personal Digital Assistants First time NetLogo user NetLogo is a programmable modeling environment It comes with a large library of existing simulations both participatory and traditional that you can use and modify Content areas include social science and economics biology and medicine physics and chemistry and mathematics and computer science You and your students can also use it to build your own simulations if you choose In tradi
121. m 2 mylist gt 6 show item 3 my shoe gt g jump jump number Turtles move forward by number units all at once without the amount of time passing depending on the distance This command is useful for synchronizing turtle movements The command forward 15 takes 15 times longer to run than forward 1 but jump 15 runs in the same amount of time as forward 1 Note When turtles jump they do not step on any of the patches along their path L last last list last string On a list reports the last item in the list On a string reports a one character string containing only the last character of the original string left It Primitives Dictionary 117 NetLogo 1 1 User Manual left number The turtle turns left by number degrees If number is negative it turns right length length list length string Reports the number of elements in the given list or the number of characters in the given string list list value1 value2 Reports a two item list containing the given items The items can be of any type produced by any kind of reporter show list random 10 random 10 gt 4 9 or similar list In In number Reports the natural logarithm of number that is the logarithm to the base e 2 71828 See also e log locals locals var1 var2 Locals is a keyword used to declare local variables in a procedure that is variables that are usable only within that procedure It must appe
122. mmands in the brackets rt random 360 is another two step command First each turtle picks a random integer between 0 and 359 random doesn t include the number you give it Then it turns right rt is short for right turn that far Heading is measured in degrees clockwise around the circle starting with 0 degrees at twelve o clock fd 1 After each turtle does that it moves forward one step in this new direction Why couldn t we have just written that in go We could but during the course of building your project it s likely that you ll add many other parts We d like to keep go as simple as possible so that it is easy to understand It could include many other things you want to have happen as the model runs such as calculating something or plotting the results Each of these sub procedures could have its own name The go button is a forever button meaning that it will continually execute its code until you shut it off by clicking on it again After you have pressed setup once to create the turtles press the go button Watch what happens Turn it off and you ll see that all turtles stop in their tracks We suggest you start experimenting with other turtle commands Type commands into the Command Window like set color rech or add them to setup go or move turtles Note that when you enter commands in the Command Center you must choose T gt P gt or O gt in the popup menu on the left depending on which agents are go
123. mylist 7 mylist is now 4 6 5 8 12 set mylist but last mylist mylist is now 4 6 8 show but first string prints tring show but last string 7 prints strin C ceiling ceiling number Reports the smallest integer greater than or equal to number show ceiling 4 5 gt 5 show ceiling 4 5 gt 4 clear all ca clear all i Kills all turtles resets all global variables to zero and calls clear patches and clear all plots clear all plots clear all plots i Clears every plot in the model See clear plot for more information clear graphics cg clear graphics Kills all turtles and clears all patches Combines the effect of clear turtles and_clear patches clear output cc Primitives Dictionary 101 NetLogo 1 1 User Manual clear output i Clears all text from the output portion of the Command Center clear patches cp clear patches Clears the patches by resetting all patch variables to their default initial values including setting their color to black clear plot clear plot In the current plot only resets all plot pens deletes all temporary plot pens resets the plot to its default values for x range y range etc and resets all permanent plot pens to their default values The default values for the plot and for the permanent plot pens are set in the plot Edit dialog which is displayed when you edit the plot If there are no plot pens after deleting all tem
124. n in pink The numbers are the total number of people in each group Do all the groups have about the same number of each sex Let s say you are having a party and invited 150 people You are wondering how people will gather together Suppose 10 groups form at the party How do you think they will group Instead of asking 150 of your closest friends to gather and randomly group let s have the computer simulate this situation for us What to do 1 Press the go button 2 Observe the movement of people until the model stops Sample Model Party 14 NetLogo 1 1 User Manual Now how many people are in each group Originally you may have thought 150 people splitting into 10 groups would result in about 15 people in each group From the model we see that people did not divide up evenly into the 10 groups instead some groups became very small whereas other groups became very large Also the party changed over time from all mixed groups of men and women to all single sex groups What could explain this There are lots of possible answers to this question about what happens at real parties The designer of this simulation thought that groups at parties don t just form randomly The groups are determined by how the individuals at the party behave The designer chose to focus on a particular variable called tolerance Tolerance is defined here as the percentage of people of the opposite sex an individual is
125. n learning NetLogo We suggest that beginning users focus on the section Tutorial 1 Running Models If you have any questions about NetLogo feel free to E mail us You can reach us at feedback ccl northwestern edu HubNet Activities Below are the current HubNet activities that are fully developed For each model you will find its educational goals and suggested ways to incorporate them into your classroom e Disease A disease spreads through the simulated population of students e Elevators Student controlled elevators demonstrate the relation of velocity and position e Function Activity Students experience the concept of a function by forming themselves into graphs e Gridlock Students use traffic lights to control the flow of traffic through a city e People Molecules Using CBR s Calculator Based Rangefinders students use their bodies to represent gas molecules e Regression As students move on screen they see the best fit line of their positions MER HubNet Guide 71 NetLogo 1 1 User Manual NOTE In addition to the discussion of learning goals and classroom techniques these materials also contain step by step instructions and screen shots As of June 2002 they are out of date and no longer match the actual activities in many respects We are working on updating them we expect these materials to be updated by July 15 2002 In the meantime please use these materials for the discussion
126. n the patches at the Primitives Dictionary 98 NetLogo 1 1 User Manual distances 2 4 1 2 and 10 15 relative to the caller mov atan atan x y Reports the arc tangent in degrees from 0 to 360 of x divided by y When y is 0 if x is positive it reports 90 if x is zero it reports 0 if x is negative it reports 270 Note that this version of atan is designed to conform to the geometry of the NetLogo world where a heading of 0 is straight up 90 is to the right and so on clockwise around the circle Normally in geometry an angle of 0 is right 90 is up and so on counterclockwise around the circle and atan would be defined accordingly show atan 1 1 gt 135 0 show atan 1 1 315 0 autoplot autoplot Reports true if auto plotting is on for the current plot false otherwise auto plot off auto plot off auto plot off auto plot on This pair of commands is used to control the NetLogo feature of auto plotting in the current plot Auto plotting will automatically update the x and y axes of the plot whenever the current pen exceeds these boundaries It is useful when wanting to display all plotted values in the current plot regardless of the current plot ranges B back bk back number The turtle moves backward by number steps If number is negative the turtle moves forward Turtles using this primitive can move a maximum of one unit per time increment So bk 0 5 and bk Primitiv
127. ncreasing decreasing or constant and 40 comes from line and curve fitting error So a value of 100 means only slope is considered while a value or 0 means only the error is considered e If you do not care about seeing strictly linear or exponential behavior in the run data you should use high relative weight values and otherwise use low ones Fitness landscape Consists of a grid of squares each of which represents the model run whose slider values were the current values of the constant sliders below and the ith and jth values of the two sliders on the grid s axes where i is the horizontal index of the square and is the vertical The entire grid thus represents all runs in which the constant sliders had their current values the current values being the ones displayed on the set of slider components held constant below the grid This grid earns the name fitness landscape because the squares of which it is composed each has a fitness value expressed by the color of the square enabling you to see a landscape of colors denoting regions of high and low fitness that is sets of neighboring near black and near blue squares The landscape represents a 2 dimensional plane in the multi dimensional parameter space of the model since it accounts for all possible values of two sliders while the rest are held constant By changing the values of any constant sliders you are shifting that 2 D plane through the parameter space and by selecting
128. nd so on Changing List Items Technically only one command changes a list set This is used in conjunction with reporters For example to change the third item of a list to 10 you could use the following code set mylist 2 7 5 Bob 3 0 2 mylist is now 2 7 5 Bob 3 0 2 set mylist replace item 2 mylist 10 mylist is now 2 7 10 Bob 3 O 2 The replace item reporter takes three inputs The first input specifies which item in the list is to be changed 0 means the first item 1 means the second item and so forth To add an item say 42 to the end of a list use the 1put reporter put adds an item to the beginning of a list set mylist lput 42 mylist mylist is now 2 7 10 Bob 3 0 2 42 But what if you changed your mind The but 1ast b1 for short reporter reports all the list items but the last set mylist but last mylist mylist is now 2 7 10 Bob 3 O 2 Suppose you want to get rid of item 0 the 2 at the beginning of the list set mylist but first mylist mylist is now 7 10 Bob 3 0 2 Suppose you wanted to change the third item that s nested inside item 3 from 2 to 9 The key is to realize that the name that can be used to call the nested list 3 0 2 is item 3 mylist Then the replace item reporter can be nested to change the list within a list The parentheses are added for clarity set mylist replace item 3 mylist replace item 2 item 3 mylist 9 mylist is now 7 10 Bob 3 0
129. nds and reporters built into NetLogo are called primitives The Primitives Dictionary has a complete list of built in commands and reporters Commands and reporters you define yourself are called procedures Each procedure has a name preceded by the keyword to The keyword end marks the end of the commands in the procedure Once you define a procedure you can use it elsewhere in your program Many commands and reporters take inputs values that the command or reporter uses in carrying out its actions Examples Here are two command procedures to setup ca 7 Clear the screen crt 10 make 10 new turtles end to go ask turtles fd 1 7 all turtles move forward one step rt random 10 ji and turn a random amount lt random 10 end Note the use of semicolons to add comments to the program Comments make your program easier to read and understand In this program setup and go are user defined commands e ca Clear all crt create turtles ask 1t left turn and xt right turn are all primitive commands random and turtles are primitive reporters random takes a single number as an input and reports a random number that is less than the input in this case between 0 and 9 turtles reports the agentset consisting of all the turtles We ll explain about agentsets later setup and go can be called by other procedures or by buttons Many NetLogo models have a once button that calls a procedure calle
130. nds on what information you want to send to the NetLogo model Further how those numbers are interpreted by the model is also up to you You can also receive data from the NetLogo model To do this use the following calculator code 4 Str6 1 gt StroO Asm prgmGETVAR Let s take a look at how the values of the string StrO are set The first input in the string represents the type of variable that you are trying to get Since we are trying to get a string Str6 we give the first input the value 4 See below for the values of legal data types The second input is the variable in which you would like to save the data received In this case we want to save the data to the variable Str6 The third input tells how you would like to save this data into this variable See below for values of valid commands It should be noted that for sending a variable the command defaults to 0 i e no command data type number 0 list of numbers 1 command number command explanation 0 No Command 1 Collate Lists into a matrix reals into a list append strings 2 Teacher Variable 4 Append Lists You should note that you must always save the information into the variable StrO when you are sending or receiving information from the calculators You can t use any other variable For more information on writing the calculator program portion of a HubNet Activity please read the on line documentation provided by TI It is und
131. new sliders to be the axes you are selecting a new plane entirely that is a plane through different dimensions e As you move your mouse over different squares in the grid the data from those runs will appear in the behavior plot to the left in addition to the line or curve that best fits the data if the add best fit line checkbox is selected e As your mouse passes over a square in the landscape information about the model run that square represents appears above the landscape This information consists of the value that each of the two selected sliders had during that run and the overall fitness of that run e The fitness of a run is an estimation of how good the run was according to the criteria you select in the menus listed above When the slope checkbox is selected fitness derives from the slope of the data as well as how well it fits a linear or exponential curve You can control the relative importance of these factors with the relative weight menu When the point statistic checkbox is selected the value that you see above the landscape is not the fitness of the run but the value of the chosen statistic For instance the minimum value of the run is shown when minimum value is selected in the point statistic type menu This value is not necessarily the fitness of the run however since the goodness of a particular value changes when you make a new selection in the point statistic value menu BehaviorSpace Guide 85 NetLogo 1
132. nobody nobody This is a special value which some primitives such as turtle random one of max one of etc return to indicate that no agent was found Also when a turtle dies it becomes equal to nobody set other random one of other turtles her if other nobody set color of other red not not boolean Reports true if boolean is false otherwise reports false if not color blue fd 10 all non blue turtles move forward 10 steps nsum nsum4 nsum patch variable nsum4 patch variable x E For each patch reports the sum of the values of patch variable in the 8 surrounding patches nsum or 4 surrounding patches nsum4 Note that nsum nsum4 are equivalent to the combination of the sum values from and neighbors neighbors4 primitives sum values from neighbors var does the same thing as nsum var sum values from neighbors4 var does the same thing as nsum4 var Therefore nsum and nsum4 are included as separate primitives mainly for backwards compatibility with older versions of NetLogo which did not have the neighbors and neighbors4 primitives See also neighbors neighbors4 Primitives Dictionary 123 NetLogo 1 1 User Manual O of VARIABLE of agent Reports the value of the VARIABLE of the given agent Can also be used to set the value of the variable set color of random one of turtles red a randomly chosen turtle turns red ask turtles set pcolor of patch at 1 0 r
133. o export Use the forward slash as the folder separator Note that the functionality of these primitives is also available directly from NetLogo s File menu export world fire csv 7 exports the state of the model to the file fire csv located in the NetLogo folder export plot Temperature c My Documents plot csv 7 exports the plot named 5 Temperature to the file plot csv located in the C My Documents folder extract hsb extract hsb color Reports a list of three values in the range 0 0 to 1 0 representing the hue saturation and brightness respectively of the given NetLogo color in the range 0 to 140 show extract hsb red gt 0 0 1 0 1 0 show extract hsb cyan gt 0 5 1 0 1 0 See also hsb rgb extract rgb Primitives Dictionary 109 NetLogo 1 1 User Manual extract rgb extract rgb color Reports a list of three values in the range 0 0 to 1 0 representing the levels of red green and blue respectively of the given NetLogo color in the range 0 to 140 show extract rgb red 1 0 0 0 0 0 show extract rgb cyan 0 0 1 0 1 0 See also rgb hsb extract hsb F first first list first string On a list reports the first Oth item in the list On a string reports a one character string containing only the first character of the original string floor floor number Reports the largest integer less than or equal to number show floor 4 5 gt Y show floor
134. ompiler sometimes incorrectly interpreted parentheses inside brackets fixed bug where turtle patch labels in the bottom row of patches could cause Java exceptions while zooming using shade of no longer causes an agent s turn to end fixed several bugs in StarLogoT model converter e interface fixes fixed bug where changes to the patch size weren t always saved with the model fixed some cases where the Errors tab didn t always highlight the location of syntax errors correctly fixed a bug where the Procedures menu could produce Java exceptions printing the procedures and info tabs now uses a smaller font size fixed Mac only bug where the Import Shapes feature sometimes behaved strangely when choosing a model fixed Linux Unix only bug where trying to create or edit a plot made NetLogo grind nearly to a halt fixed bug on Java 1 4 VM s where the Tab key didn t work in the Command Center and Procedures tab now on Macs subsequent Java exceptions after the first are no longer lost when running under Classic on OS X 10 2 the User Manual menu item on the Help menu now works and launches your default browser instead of always Internet Explorer when running native on OS X 10 2 which is not officially supported yet the Quit menu item now asks you if you want to save your changes like it should e fixes to Save as Applet feature improved instructions in saved applets and made them visible HTML text instead of invisible HT
135. on other platforms use the right mouse button agent monitors are now their own floating windows agent command centers now do syntax highlighting and support command history code editor now auto indents a new line to the same level as the line above it arrow keys in combination with option key Mac or control key other OS s now moves word by word tab key now cycles the Command Center between Observer Turtles and Patches sliders now have an optional units field performance improvements made so models run faster most models only a little faster but some substantially new turtle graphics options note using these options slows down most models a lot we hope to improve this in a future version 0 new turtle variable called size edit the Graphics Window and check the Turtle Sizes checkbox to enable scaling of turtles according to this variable 0 new Exact Turtle Positions checkbox edit the Graphics Window and check this box to enable drawing of turtles in their exact positions instead of always in the center of their patch as is the default language changes new primitive without interruption lets you mark a section of code as being executed all at once without any other agents being able to interrupt new primitives neighbors and neighbors4 return an agentset of a turtle s or patch s eight or four neighboring patches new primitive inspect lets you open an agent monitor for any turtle or patch new primitives user
136. one fd 1 77 to go forward ask turtle 1 tell the second one set color green 77 tO become green ask turtle 2 tell the third one rt 90 5 vato curn right ask patch 2 2 ask the patch at coords 2 2 set pcolor blue jj to become blue ask turtle 0 ask the first turtle ask patch at 1 0 77 to ask patch to the east set pcolor red to become red end Every turtle created has an ID number The first turtle created has ID 0 the second turtle ID 1 and so forth The turt 1e primitive reporter takes an ID number as an input and reports the turtle with that ID number The patch primitive reporter takes values for pxcor and pycor and reports the patch with those coordinates And the patch at primitive reporter takes offsets distances in the x and y directions from the first agent In the example above the turtle with ID number 0 is asked to get the patch east and no patches north of itself You can also select a subset of turtles or a subset of patches and ask them to do something This involves a concept called agentsets The next section explains this concept in detail Agentsets An agentset is exactly what its name implies a set of agents An agentset can contain either turtles or patches but not both at once You ve seen the turtles primitive which reports the agentset of all turtles and the patches primitive which reports the agentset of all patches But what s powerful about the ag
137. ou try to have the observer ask patch 0 set pcolor blue you ll get an error message Command Center Clear ERROR For second input to PATCH expected a number but got a list or block instead To ask an individual turtle to do something we use its ID number But patches don t have ID numbers therefore we need to refer to them some other way Remember patches are arranged on a coordinate system Two numbers are needed to plot a point on a graph an x axis value and a y axis value Patch locations are designated in the same way as plotting a point Open a patch monitor for any patch The monitor shows that for the patch in the picture its pxcor variable is 5 and its pycor Variable is 4 If we go back to the analogy of the coordinate plane and wanted to plot this point the point would be found in the upper left quadrant of the coordinate plane where x 5 and y 4 To tell this particular patch to change color use its coordinates e Type ask patch 5 4 set pcolor blue and press return What are the two words in this command that tip you off that we are addressing a patch What s Next At this point you may want to take some time to try out the techniques you ve learned on some of the other models in the Models Library Tutorial 2 Commands 33 NetLogo 1 1 User Manual In_Tutorial 3 Procedures you can learn how to alter and extend existing models and build your own models Tutorial 2 Comm
138. ous activity we used the set command to change the colors of all the cars But if you recall the original model contained one red car amongst a group of blue cars Let s look at how to change only one car s color e Press setup to get the red car to reappear e f you are on a Macintosh hold down the Control key and click on the red car On other operating systems click on the red car with the right mouse button e From the popup menu that appears choose inspect turtle 0 A turtle monitor for that car will appear Taking a closer look at this turtle monitor we can see all of the variables that belong to the red car A variable is a place that holds a value that can be changed Remember when it was mentioned that all colors are represented in the computer as numbers The same is true for the agents Let s take a closer look at the turtle monitor What is this turtle s ID number What color is this turtle What shape is this turtle Tutorial 2 Commands 31 NetLogo 1 1 User Manual This turtle monitor is showing a turtle who that has an ID number of O a color of 15 red see above chart and the shape of a car There are three ways to change an individual turtle s color One way is to use the box found at the bottom of the monitor also called an Agent Commander You type commands here just like in the Command Center but the commands you type here are only done by this particular turtle eTy
139. pe rabbit In the command center give this command to the observer crt 50 And then give these commands to the turtles to spread them out then change their shape fd random 15 set shape rabbit Voila Rabbits Note the use of quotation marks around the shape name The set default shape primitive is also useful for assigning shapes to turtles Shapes Editor Guide 78 BehaviorSpace Guide This guide is broken up into three parts e What is BehaviorSpace A general description of the tool including the ideas and principles behind it How it Works Walks you through how to use the tool and highlights its most commonly used features e Interface Reference Offers comprehensive descriptions of each main window as well as the interface components within those windows What is BehaviorSpace BehaviorSpace is a software tool integrated with NetLogo that allows you to perform experiments with models It systematically varying the values of sliders and records the results of each corresponding model run This way you can explore the model s space of possible behaviors and determine which combinations of slider values cause the behaviors of interest The need for this type of experiment is revealed by the following observations Models often have more than one slider each of which can take a large range of values Together they form what in mathematics is called a parameter space for the model whose dimensions are the numb
140. pe set color pink What happens in the Graphics Window Did anything change in the Turtle Monitor A second way to change one turtle s color is to go directly to the color variable in the Turtle Monitor and change the value e Select the text to the right of color in the Turtle Monitor e Type in a new color such as green 2 What happened There are two other ways to open a turtle monitor besides the one you just did One way is to choose Turtle Monitor from the Tools menu then type the ID number of the turtle you want to inspect into the who field The other way is to type inspect turtle 0 or other ID number into the Command Center You close a turtle or patch monitor by clicking the close box in the upper left hand corner Macintosh or upper right hand corner other operating systems Just as there are Turtle Monitors there are also Patch Monitors Can you make a patch monitor and use it to change the color of a single patch The third way to change an individual turtle s or patch s color is to use the observer Since the observer oversees the NetLogo world it can give commands that affect individual turtles or patches as well as groups of turtles or patches e n the Command Center select Observer from the popup menu or use the tab key eTypeask turtle 0 set color blue and press return What happens Tutorial 2 Commands 32 NetLogo 1 1 User Manual Can you turn one patch blue If y
141. population model Open the Models Library from the File menu it Edit Tools Zoom Models Library 38M R aes Save As Save As Applet Print P Export World Export Plot Export Output Import World Quit 36Q e Choose Wolf Sheep Predation from the Biology section and press Open The Interface tab will fill up with lots of buttons switches sliders and monitors These interface elements allow you to interact with the model Buttons are blue they set up start and stop the model Sliders and switches are green they alter model settings Monitors and plots are beige they display data When you first open the model you will notice that the Graphics Window is empty all black To begin the model you will first need to set it up e Press the setup button What do you see appear in the Graphics Window e Wait until the setup button pops back up in other words turns blue again e Press the go button to start the simulation As the model is running what is happening to the wolf and sheep populations Tutorial 1 Models 17 NetLogo 1 1 User Manual e Press the go button to stop the model Controlling the Model Buttons When a button is pressed the model responds with an action A button can be a once button or a forever button You can tell the difference between these two types of buttons by a symbol on the face of the button Forever buttons have two arrows in t
142. porary pens that is to say if there are no permanent plot pens a default plot pen will be created with the following initial settings e Pen down e Color black Mode 0 line mode e Name default e Interval 1 0 See also_clear all plots clear turtles ct clear turtles i Kills all turtles See also die COS Primitives Dictionary 102 NetLogo 1 1 User Manual cos number Reports the cosine of the given angle Assumes the angle is given in degrees show cos 180 gt 1 0 count count agentset Reports the number of agents in the given agentset show count turtles 7 prints the total number of turtles show count patches with pcolor red 7 prints the total number of red patches create turtles crt create BREED create turtles number create BREED number KI Creates number new turtles New turtles start at position 0 0 are created with the 14 primary colors and have headings from 0 to 360 evenly spaced crt 100 ask turtles fd 10 makes an evenly spaced circle If the create lt BREED gt form is used the new turtles are created as members of the given breed create custom turtles cct create custom BREED cct BREED create custom turtles number commands create custom BREED number commands i Creates number new turtles of the given breed if specified New turtles start at position 0 0 New turtles are created with the 14 primary
143. ppies See also globals patches own breeds lt BREED gt own type type value Prints value in the Command Center not followed by a carriage return unlike print and show The lack of a carriage return allows you to print several values on the same line The calling agent is not printed before the value unlike show type 3 type print 4 gt 34 See also print show U uphill uphill patch variable x Reports the turtle heading between 0 and 359 degrees in the direction of the maximum value of the variable patch variable of the patches in a one patch radius of the turtle This could be as many as eight or as few as five patches depending on the position of the turtle within its patch If there are multiple patches that have the same greatest value a random one of those patches will be selected If the patch is located directly to the north south east or west of the patch that the turtle is currently on a multiple of 90 degrees is reported However if the patch is located to the northeast northwest southeast or southwest of the patch that the turtle is currently on the direction the turtle would need to reach the nearest corner of that patch is reported See also uphill4 downhill downhill Primitives Dictionary 143 NetLogo 1 1 User Manual uphill4 uphill4 patch variable x Reports the turtle heading between 0 and 359 degrees as a multiple of 90 degrees in the direction
144. pxcor and pycor must be integers ask patch 3 4 set pcolor green patch with pxcor of 3 and pycor of 4 turns green See also patch at patch at patch at dx dy patch at reports the single patch at dx dy from the caller that is dx patches east and dy patches north of the caller If the caller is the observer the given offsets are computed from the origin ask patch at 1 1 set pcolor green lf caller is the observer turn the patch 3 at 1 1 green lf caller is a turtle or patch turns the CR patch just southeast of the caller green See also_patch patch here patch here patch here reports the patch under the turtle Primitives Dictionary 125 NetLogo 1 1 User Manual patches patches Reports the agentset consisting of all patches patches own patches own var1 var2 This keyword like the globals breeds lt BREED gt own and turtles own keywords can only be used at the beginning of a program before any function definitions It defines the variables that all patches can use All patches will then have the given variables and be able to use them See also globals turtles own breeds lt BREED gt own pen down pd pen up pu pen down pen up The turtle its pen down or up so that it draws leaves a trail when they move or doesn t Turtles draw by changing the color of the patches underneath them to their own color To change the color of the turtle s pen
145. r curve can be added along with the data if the add best fit line checkbox is selected e Run data can be continually collected in the plot and superimposed on each other by selecting the superimpose plots checkbox e Only 14 plot pen colors are used so if more than 14 data sets are superimposed at a single time the system will begin reusing colors for the new pens e Automatically scales to show all data Add best fit line checkbox Adds the line or exponential curve that best fits the data to the behavior plot depending on whether linear or exponential was selected in the slope type menu Superimpose plots checkbox Stops old data from being removed from the behavior plot when new data is added resulting in increasing sets of data being superimposed on each other Unselected the checkbox causes all data to be removed Export Plot button Saves the data currently being displayed in the behavior plot to a file Export Behavior Data button Saves the behavior data gathered during all of the model runs to a file The data saved for each model run includes the slider settings for that run how many time ticks the run lasted the minimum maximum average and final value for the behavior reporter and the value of the behavior reporter at each time tick during the run Note that the fitnesses are not exported only the raw behavior data In a future version of BehaviorSpace the fitness data will be exported as well Note The export bu
146. rapping around the edges of the screen downhill Primitives Dictionary 106 NetLogo 1 1 User Manual downhill patch variable Reports the turtle heading between O and 359 degrees in the direction of the minimum value of the variable patch variable of the patches in a one patch radius of the turtle This could be as many as eight or as few as five patches depending on the position of the turtle within its patch If there are multiple patches that have the same smallest value a random one of those patches will be selected If the patch is located directly to the north south east or west of the patch that the turtle is currently on a multiple of 90 degrees is reported However if the patch is located to the northeast northwest southeast or southwest of the patch that the turtle is currently on the direction the turtle would need to reach the nearest corner of that patch is reported See also downhill4 uphill uphill4 downhill4 downhill4 patch variable Reports the turtle heading between 0 and 359 degrees as a multiple of 90 degrees in the direction of the minimum value of the variable patch variable of the four patches to the north south east and west of the turtle If there are multiple patches that have the same least value a random patch from those patches will be selected See also downhill uphill uphill4 dx dy dx dy Reports the x increment or y increment if the turtle were to take one step for
147. rigin values from values from agentset reporter Reports a list that contains the value of the reporter for each agent in the agentset ca crt 4 show values from turtles who gt 01 2 3 show values from turtles who who gt 0 1 4 9 variance variance list Reports the unbiased statistical variance of a ist of numbers Ignores other types of items show variance 2 7 4 3 5 gt 3 7 W wait wait number Wait the given number of seconds You can use floating point numbers to specify fractions of seconds Note that you can t expect complete precision the agent will never wait less than the given amount but might wait slightly more repeat 10 fd 1 wait 0 5 See also every Primitives Dictionary 145 NetLogo 1 1 User Manual while while reporter commands If reporter reports false exit the loop Otherwise run commands and repeat The reporter may have different values for different agents so some agents may run commands a different number of times than other agents while any other turtles here fd 1 turtle moves until it finds a patch that has no other turtles on it with agentset with reporter Takes two inputs on the left an agentset usually turtles or patches On the right a boolean reporter Reports a new agentset containing only those agents that reported true in other words the agents satisfying the given condition show count patches wit
148. rints the patch with the most turtles on it mean mean list Reports the statistical mean of the numeric elements of the given list Ignores non numeric elements The mean is the average e the sum of the elements divided by the total number of elements show mean values from turtles xcor 7 prints the average of all the turtles x coordinates median median list Reports the statistical median of the numeric elements of the given list Ignores non numeric elements The median is the item that would be in the middle if all the items were arranged in order If two items would be in the middle the median is the average of the two show median values from turtles xcor prints the median of all the turtles x coordinates member member value list member string1 string2 For a list reports true if the given value appears in the given list otherwise reports false For a string reports true or false depending on whether string1 appears anywhere inside string2 as a substring show member 2 1 2 3 gt true show member 4 1 2 3 gt false show member rin string gt true See also_position min min list Reports the minimum number value in the list It ignores other types of items show min values from turtles xcor prints the lowest x coordinate of all the turtles Primitives Dictionary 120 NetLogo 1 1 User Manual min one of min one of agentset reporter Report
149. ry A collection of demonstration models MA to save models As Save As Applet Used to save a web page in HTML format that has your model embedded in itas a Java applet Print Sends the contents of the currently showing tab to your printer Export World Saves all variables and the current state of all turtles and patches to a file ExportPlot Saves the data in a plot to a file Export Output Save the contents of the output section of the command center to a file Import Word Load a file that was saved by Export Wad Interface Guide 49 NetLogo 1 1 User Manual Quit Exits NetLogo eat 7 Undo that last action user performed Cut Cuts out or removes the selected text and temporarily saves it to the lipboard Cop Copies the selected text L Pee RE RM ENDE the clipboard text where cursor is currently located Delete Deletes selected text selected text zem Find Finds a word or sequence of characters within the text windows Find Again Again ill find the next occurrence of the word or sequence Toots Monitor Displays the values of all global variables Patch Monitor Displays the values of all of the variables in a particular patch You can can also edit the values of the patch s variables and issue commands to the patch You can also open a patch monitor via the Graphics Window see the Graphics Window section below urtle Monitor Displays the values of all of the variables
150. s 19 9 is white but 20 0 is black The available color names are listed below See also the rgb and hsb primitives Primitives Dictionary 96 NetLogo 1 1 User Manual black 0 gray 5 white 9 999 red 15 orange 25 brown 35 yellow 45 green 55 lime 65 turquoise 75 cyan 85 sky 95 blue 105 violet 115 magenta 125 pink 135 A abs abs number Reports the absolute value of number show abs 7 gt 7 show abs 5 gt 5 and condition and condition2 Reports true if both condition and condition2 are true Note that if condition is false then condition2 will not be run since it can t affect the result if pxcor gt 0 and pycor gt 0 set pcolor blue the upper right quadrant of 7 patches turn blue any any agentset Reports true if the given agentset is non empty false otherwise Equivalent to agentset gt 0 but more readable and may run faster as well if any turtles with color red Primitives Dictionary 97 NetLogo 1 1 User Manual show at least one turtle is red Arithmetic Operators 2 lt gt ls lt gt All of these operators take two inputs and all act as infix operators going between the two inputs as in standard mathematical use NetLogo correctly supports order of operations for infix operators The operators work as follows is addition is multiplication is subtraction is division
151. s but for step by step instructions rely instead on the QuickStart Instructions built into the activities see next section Running an activity You ll find the HubNet activities in NetLogo s Models Library under the HubNet Activities folder When you open the first HubNet activity for each session of NetLogo you will be prompted by a login dialog This prompts you to enter information such as User Id and Password that is necessary for connecting to the appropriate server and running the HubNet activity If you don t actually want to run the model just press the Cancel button Be aware you may still get NetLogo Runtime errors if you do press cancel In each of the activities you ll see a box on the screen labeled QuickStart Instructions It contains step by step instructions on how to run that activity Click the Next gt gt gt button to advance to the next instruction We suggest doing a few practice runs of the activity before trying it in front of an actual class If you have any questions about running the activities feel free to E mail us You can reach us at feedback ccl northwestern edu Proxy web servers and firewalls If your school uses a proxy web server or a firewall you must use the NetLogo applet not the NetLogo application You may need to adjust the preferences in your browser to let it know about your proxy server or firewall If you are not sure if your school uses a proxy web server or firewall or
152. s AAA 18 Gathering Information Plots and Montar naaa 20 e 20 eine 21 Changing Graphics A es aeo e ne ee een ever e iets eere gd 21 TRA Models IBA RO eem 24 SAMPE MARIS ore arco ici 24 Code ER sintio RR 24 HubNet Activities 24 MR dE tue REO MED DERI aaa an ERE COREL SPARTE NAE ERN EFE Ieee 25 Codice sc DC TEES 25 Edi Ere COMON EDU LE I NU 26 Sample Model Talie PAI aida 26 ThE Command Cani ta aia 26 bor da Eli A E TNNT Em 29 Agent Monitors and Agent CGommanders A 31 e E EE 33 WUHAN SS die LE 35 Senp and LS Oe ee ee enter ee aE T 35 Parches and OS ce rie cese perdre d eiie tib afa iv ne E REPE mda PV vea e EUM E Hp Pee uy e atri vana ecd 38 ARNM Eet Bl HIE EO Et 41 A AA E A T N TARE ETE RR 45 Ahas is ict ERE TERRE DD m 46 Appendix COI LOA TT 46 Merce Er EE 49 nn LUE D EE 49 da ATRIDES REC 50 dide Mem T 51 UN VOT usn O 54 Amiens oi TaD EE 55 esie o RC on oi 55 Programming ti ti TT t 57 EOS c ucc E E ML DM ID Lu MM I d ELE ea LL 57 A EEE E TEAT E E A A ATAT 58 A A A 59 A A ate 60 Pe RO D TER 61 AUS 62 A NUON OSU EE Ee E E Sere rea mee rrr Sart 64 Er MRM t TT TOTO TT A 65 Proc dures Ee ace icr Mi 65 NetLogo 1 1 User Manual Table of Contents Programming Guide rome oe ose gee oe 66 SUE RENT ROT Tete 67 A UNES LIEST 68 sie ea aC e sere ee ee SEL I c E 70 PROM EN E A AA A ts 70 What do need to g t KE
153. s ccl northwestern edu Application or Applet There are two ways to run NetLogo e Download application This enables you to run NetLogo as a normal application Size of download usually between 8 and 14 megabytes depending on options e Run applet on the web within your browser window Running on the web is convenient but downloading the application has some significant advantages Fewer compatibility issues with various operating systems and browsers e Starts up faster and models run faster e Window is resizable e Edit menu is available e Keyboard shortcuts for menu items are available System Requirements Application On any type of computer a Java Virtual Machine that supports Java version 1 1 or later is required On the Windows MacOS and Linux platforms you can choose to include the Java Virtual Machine with the download On all systems approximately 15MB of free hard drive space is required Windows e Windows 95 NT 98 ME 2000 or XP e 64 MB RAM Macintosh OS X e OS version 10 1 or later e 128 MB RAM Macintosh OS 8 x or 9 x e PowerPC processor e OS version 8 1 or later 8 5 or later recommended e 64 MB RAM 96 MB RAM recommended System Requirements 8 NetLogo 1 1 User Manual Other platforms NetLogo should work on any platform on which a Java Virtual Machine version 1 1 or later is available If you have trouble please contact us see above System Requirements Applet Your
154. s each turtle looks at the variable elevation in the patch on which the turtle would be if it went forward 1 If the test is true the turtle moves itself forward 1 The test is necessary because if the turtle is already on the peak we don t want it to move off it Go ahead and type that in but before you test it out by pressing the go button ask yourself this question what do you think will happen Try and predict how a turtle will move where it will go and how long it ll take to get there When you re all set press the button and see for yourself Not too exciting Surprised Try to understand why the turtles converge to their peaks so quickly Maybe you don t believe the algorithm we ve chosen works correctly There s a simple change you can make to test it rewrite setup patches so that it says to setup patches ask patches set elevation pycor set pcolor scale color green elevation 0 Screen edge y screen edge y end Now run the project See that the turtles all head for the highest elevation the top of the screen Another common tool to see what s going on is to write T gt pd in the Command Center Then each turtle traces its path with its color and you can observe its path Our turtles rapidly arrive at local maxima in our landscape Local maxima and minima abound in a randomly generated landscape like this one Our goal is to still get the turtles to find an optimal maximum one of the white patches We n
155. s the agent in the agentset that reports the lowest value for the given reporter show min one of turtles xcor ycor reports the turtle with the smallest sum of its coordinates mod number1 mod number2 Reports number modulo number2 that is the remainder when number is divided by number Note that mod is infix that is it comes between its two inputs show 62 mod 5 xou mouse down mouse down Reports true if the mouse button is down false otherwise Note If the mouse pointer is outside of the NetLogo graphics window mouse down will always report false mouse xcor mouse ycor mouse xcor mouse ycor Reports the x or y coordinate of the mouse in the Graphics Window The value is in terms of turtle coordinates so it is a floating point number If you want patch coordinates use round mouse xcor and round mouse ycor Note If the mouse is outside of the NetLogo graphics window reports the value from the last time it was inside to make the mouse draw in red if mouse down set pcolor of patch at mouse xcor mouse ycor red Primitives Dictionary 121 NetLogo 1 1 User Manual myself myself isd When an agent has been asked by a turtle to run some code using myself in that code reports the agent turtle or patch that did the asking myself is most often used in conjunction with of to read or set variables in the asking agent myself can be used within blocks of code not just in the
156. s this variable First each patch picks a random number between 0 and 9999 inclusive and sets its elevation value to that number We then use an observer primitive diffuse that essentially smooths out the distribution of this variable over the neighboring patches We can see the effect of diffuse in the next command which uses scale color a reporter uses the different values of elevation to assign colors to the patches In this case we re assigning different shades of green to all the patches Don t worry about the numbers given to diffuse and scale color just yet The larger elevation is the lighter the shade of green Low values of elevation will result in darker shades Setup turtles is familiar being exactly what we were doing in our old setup Type this in and press the setup button Voila a lush NetLogo patch landscape Tutorial 43 Procedures 39 NetLogo 1 1 User Manual Here s how you can see how diffuse works Return to the Procedures Window and comment out the diffuse command by adding a semicolon in front of it like this diffuse elevation 1 Press setup again doesn t look as good does it This is because as mentioned above diffuse has each patch share its value of elevation with all its neighbors by having every patch reset its value of elevation to a new value that depends on the value of elevation all around it Don t worry if you don t exactly understand what s going on here You can rea
157. ses If you encounter a specific instance of this problem and are not sure whether it falls into the blame NetLogo category or the blame floating point arithmetic in general category run it by us and we ll take a look Is there some simple way to multiply one list by another list or number without writing a procedure At present no We plan to add this capability in a future version Can read data from a file At present this is only possible through the Import World mechanism but you can t read files containing arbitrary data We plan to add this capability in a future version of NetLogo In the meantime you may find the following workarounds useful 1 Copy and paste the data into the Procedures window store it in a variable and then deal with it from there 2 Use Import World to import the data This will require modifying your data to be in the format that import world expects You can use Export World to produce an example of the format and then use that as a template How does NetLogo decide when to switch from agent to agent when running code Turtles are scheduled for execution in ascending order by ID number Patches are scheduled for execution by row left to right within each row and starting with the top row In a future version of NetLogo we plan to add an option for randomized scheduling Once scheduled an agent s turn ends only once it performs an action that affects the state of the world such
158. set of primitives hubnet reset hubnet message waiting hubnet fetch message hubnet message hubnet message source What s New 5 NetLogo 1 1 User Manual hubnet message tag hubnet broadcast hubnet set tags hubnet set client interfac Version 1 0 April 2002 e User Manual redesigned and expanded e permanent plot pens e miscellaneous fixes and improvements Beta 10 March 2002 e models using turtle and patch labels run faster e improved compiler and runtime errors and error handling e usability improvements to Command Center e full string processing capabilities e plotting modes line bar and point e miscellaneous fixes and improvements Beta 9 December 2001 e models run faster now e syntax highlighting editor new language support for working with agents individually e Import World e integer sliders e Edit menu e miscellaneous fixes and improvements Beta 8 October 2001 e miscellaneous fixes and improvements Beta 7 September 2001 e models that use turtle shapes now run much faster e much larger numbers of agents now supported e more colorful amp attractive interface e runtime errors e Zoom In and Zoom Out for easy viewing histograms breed specific turtle variables e patch labels e true integer arithmetic random seed primitive for repeatable model runs e miscellaneous fixes and improvements What s New NetLogo 1 1 User Manual Beta 6 August 200
159. slider to 100 e Set the init wolves slider to 20 e Press setup and then go e Let the model run for about 100 ticks What happened to the sheep population Did this outcome surprise you What other sliders or switches can be adjusted to help out the sheep population e Set sheep reproduce to 10 0 e Press setup and then go e Let the model run for about 100 ticks What happened to the wolves in this run When you open a model all the sliders and switches are on a default setting If you open a new model or exit the program your changed settings will not be saved unless you choose to save them Gathering Information Plots and Monitors The purpose to modeling is to gather data on a subject or topic that would be very difficult to do in a laboratory situation NetLogo has two main ways of displaying data to the user plots and monitors Plots The plot in Wolf Sheep Predation contains three lines wolf sheep and grass The lines show what s happening in the model over time To see which line is which click on Pens in the upper right Tutorial 41 Models 20 NetLogo 1 1 User Manual corner of the plot window to open the plot pens legend A key appears that indicates what each line is plotting In this case it s the population counts Note the grass count is divided by four so it doesn t make the graph too tall If you want to save the data from a plot to view or analyze it in another program you can us
160. stern edu ps Center for Connected Learning and Computer Based Modeling Northwestern University Evanston IL How do cite a model from the Models Library in an academic publication Wilensky U year Name of Model URL of model Center for Connected Learning and Computer Based Modeling Northwestern University Evanston IL To determine the URL for a model visit our web based version of the Models Library and click on the name of the model An example model URL is htto ccl northwestern edu netlogo models PepperedMoths To determine the year open the model from the NetLogo application and look in the copyright information at the bottom of the Procedures tab What license is NetLogo released under Are there are any legal restrictions on use redistribution etc The NetLogo software models and documentation are distributed free of charge for use by the public to explore and construct models Permission to copy or modify the NetLogo software models and documentation for educational and research purposes only and without fee is hereby granted provided that this copyright notice and the original author s name appears on all copies and supporting documentation For any other uses of this software in original or modified form including but not limited to distribution in whole or in part specific prior permission must be obtained from Uri Wilensky The software models and documentation shall not be used rewritten or adapted as
161. t 0 number end Primitives Dictionary 140 NetLogo 1 1 User Manual to report first turtle report who 0 reports true or false end towards towards nowrap towards agent towards nowrap agent Reports the heading from this agent to the given agent If the wrapped distance around the edges of the screen is shorter than the on screen distance towards will report the heading of the wrapped path towards nowrap never uses the wrapped path towardsxy towardsxy nowrap towardsxy x y towardsxy nowrap x y Reports the heading from the turtle or patch towards the point x y If the wrapped distance around the edges of the screen is shorter than the on screen distance towardsxy will report the heading of the wrapped path towardsxy nowrap never uses the wrapped path turtle turtle number Reports the turtle with the given ID number or nobody if there is no such turtle number must be an integer set color of turtle 5 red turtle with id number 5 turns red ask turtle 5 set color red another way to do the same thing turtles turtles Reports the agentset consisting of all turtles show count turtles prints the number of turtles Primitives Dictionary 141 NetLogo 1 1 User Manual turtles at BREED at turtles at dx dy BREED at dx dy Reports an agentset containing the turtles on the patch dx dy from the caller including the caller itself if it s a turtle If the caller
162. t pen interval also affects the behavior of the histogram and histogram list commands set plot pen mode set plot pen mode number Sets the mode the current plot pen draws in to number The allowed plot pen modes are e 0 line mode the plot pen draws a line connecting two points together e 1 bar mode the plot pen draws a bar of width plot pen interval with the point plotted as the upper or lower if you are plotting a negative number left corner of the bar e 2 point mode the plot pen draws a point at the point plotted Points are not connected The default mode for new pens is 0 line mode set plot x range set plot y range set plot x range min max set plot y range min max Sets the minimum and maximum values of the x or y axis of the current plot The change is temporary and is not saved with the model When the plot is cleared the ranges will revert to their default values as set in the plot s Edit dialog setxy setxy X y The turtle sets its x coordinate to x and its y coordinate to y Equivalentto set xcor x set ycor y exceptit happens in one time step instead of two Primitives Dictionary 136 NetLogo 1 1 User Manual setxy 0 0 7 turtle moves to the middle of the center patch shade of shade of color color2 Reports true if both colors are shades of one another false otherwise show shade of blue red gt false show shade of blue blue 1 gt true show shade of gray white gt tru
163. tems Ask NetLogo uses the ask command to specify commands that are to be run by turtles or patches All code to be run by turtles must be located in a turtle context You can establish a turtle context in any of three ways e In a button by choosing Turtles from the popup menu Any code you put in the button will be run by all turtles e In the Command Center by choosing Turtles from the popup menu Any commands you enter will be run by all the turtles e By using ask turtles The same goes for patches and the observer except that code to be run by the observer must not be inside any ask Here s an example of the use of ask syntax in a NetLogo procedure to setup ca Programming Guide 61 NetLogo 1 1 User Manual ert 100 create 100 turtles ask turtles set color red turn them red rt random 360 give them random headings fd 50 7 Spread them around ask patches if pxcor gt 0 77 patches on the right side set pcolor green of the screen turn green end The models in the Models Library are full of other examples A good place to start looking is in the Code Examples section Usually the observer uses ask to ask all turtles or all patches to run commands You can also use ask to have make an individual turtle or patch run commands The reporters turtle patch and patch at are useful for this technique For example to setup ca crt 3 make 3 turtles ask turtle 0 tell the first
164. terize in RGB terms show rgb 0 0 0 gt 0 black show rgb 0 1 0 1 0 gt 85 cyan See also extract rgb hsb and extract hsb right rt right number The turtle turns right by number degrees If number is negative it turns left round round number Reports the integer nearest to number If the decimal portion of number is exactly 5 the number is rounded in the positive direction Note that rounding in the positive direction is not always how rounding is done in other software programs In particular it does not match the behavior of the StarLogoT which always rounded numbers ending in 0 5 to the nearest even integer The rationale for this behavior is that it matches how turtle coordinates relate to patch coordinates in NetLogo For example if a turtle s xcor is 4 5 then it is on the boundary between a patch whose pxcor is 4 and a patch whose pxcor is 5 but the turtle must be considered to be in one patch or the other so the turtle is considered to be in the patch whose pxcor is 4 because we round towards the positive numbers show round 4 2 gt 4 Primitives Dictionary 132 NetLogo 1 1 User Manual show round 4 5 gt 5 show round 4 5 gt 4 S scale color scale color color number range1 range2 Reports a shade of color proportional to number If range is less than range2 then the larger the number the lighter the shade of color But if range2 is less than range7 the color scalin
165. th the remove last button The remove last and remove all buttons are the only way of correcting mistakes you can t go back to move or alter the shape after it s been drawn If you make a mistake to fix it remove and redraw the shape Areas that use the key color selected from a drop down menu the default is gray will change according to the value of each turtle s color variable in your model Areas filled with any other color selected from the palette at the top will stay that color regardless of each turtle s color For example you could create cars that always have yellow headlights and black wheels but have bodies of different colors to make this happen you would draw the bodies in the key color It s tempting to draw complicated interesting shapes but remember that in most models the patch size is so small that you won t be able to see all the detail Simple bold shapes are best When the shape is done give it a name and click on the save option at the bottom of the screen The shape and its name will now be in the list along with the default shape If you want to borrow a shape from another model use the import button to call up other NetLogo models and import shapes from them Shapes Editor Guide 77 NetLogo 1 1 User Manual Using Shapes in a Model After closing the shapes editor you can adjust the code to call the new shape For example suppose you want to create 50 turtles with the sha
166. the item to be replaced starting with O The 6th item in a list would have an index of 5 Note that replace item is used in conjunction with set to change a list Likewise for a string but the given character of string1 removed and the contents of string2 spliced in instead show replace item 2 2 7 4 5 15 gt 27155 show replace item 1 sat o gt slot report report value Immediately exits from the current to report procedure and reports value as the result of that procedure report and to report are always used in conjunction with each other See to report for a discussion of how to use them reset timer reset timer Resets the global clock to zero See also timer reverse reverse list reverse string Reports a reversed copy of the given list or string show mylist mylist is 2 7 4 Bob Primitives Dictionary 131 NetLogo 1 1 User Manual set mylist reverse mylist 7 mylist now is Bob 4 7 2 show reverse string gt gnirts rgb rgb red green blue Reports a number in the range 0 to 140 not including 140 itself that represents the given color specified in the RGB spectrum in NetLogo s color space All three inputs should be in the range 0 0 to 1 0 The color reported may be only an approximation since the NetLogo color space does not include all possible colors See_hsb for a description of what parts of the HSB color space NetLogo colors cover this is difficult to charac
167. tion tab provides an introduction to the model and an explanation of how to use it things to explore possible extensions and NetLogo features It is very helpful when you re first exploring a model JE o V ASA es e 2 Find Find Again WHAT IS IT This model explores the stability of predator prey ecosysten is described in two papers by Wilensky amp Reisman referenced unstable when they tend to result in extinction for one or n contrast systems are stable when they tend to maintain then fluctuations in population sizes There are two main variati In the first variation wolves and sheep wonder randomly arc wolves look for sheep to prey on Each step costs the wolves in order to replenish their energy when they run out of er population to continue each wolf or sheep has a fixed probc We recommend reading the Information Tab before starting the model The Information Tab explains what principle is being modeled and how the model was created Errors Tab The Errors Tab provides a place for errors to be highlighted and brought to your attention If there are any errors in your code the Errors Tab will turn red and come to the front with an explanation of what caused the error Interface Guide 55 NetLogo 1 1 User Manual set default shape wolves wolf shape create custom wolves init wolves create the wolves then ini ZET set energy random 2 wolf metabolism setxy random screen size x random screen siz
168. tional NetLogo simulations the simulation runs according to rules that the simulation author specifies HubNet adds a new dimension to NetLogo by letting simulations run not just according to HubNet Guide 70 NetLogo 1 1 User Manual rules but by direct human participation Since HubNet builds upon NetLogo we recommend that before trying HubNet for the first time you should be familiar with the basics of NetLogo Teacher workshops For information on up and coming workshops and NetLogo and HubNet use in the classroom please contact us at feedback 2ccl northwestern edu Getting Started With HubNet Using NetLogo We recommend that you become familiar with NetLogo itself before using the HubNet technology You can run NetLogo in either of two ways e Run the NetLogo application which you can download and install from the NetLogo web site e Run the NetLogo applet in your browser at our web site The application starts up faster and has some extra features However if your school has firewalls or proxy servers consult the Proxy Web Servers amp Firewalls section below You can become familiar with NetLogo by trying out some of the models in the Models Library Open the Models Library from the File menu in NetLogo Then click on a model that you want to try and press the Open button The Information tab in each of the models gives background information and instructions Other sections of the NetLogo User Manual may be helpful whe
169. to select pilot sites but Tl has announced that it will be commercially available in January 2003 Can I run a NetLogo model from the command line Can I run it without a GUI At present there is no way to run without the GUI We plan to add this in a future version Automating runs from the command line is possible but currently not officially supported or documented If you need this for your work it can be done but some light Java programming is required We can supply sample Java code that you can alter for your needs Anyone interested in doing this write us at feedback 2ccl northwestern edu Programming How is the NetLogo language different from the StarLogoT language How do convert my StarLogoT model to NetLogo We don t have a document that specifically summarizes the differences We suggest reading the Programming Guide section of this manual particularly the sections on Ask and Agentsets Looking at some of the sample models and code examples in the Models Library may help as well If you need any help converting your StarLogo or StarLogoT model to NetLogo please feel free to get in touch with us at_feedback ccl northwestern edu The NetLogo Users Group is also a good FAQ Frequently Asked Questions 91 NetLogo 1 1 User Manual resource for getting help from other users The NetLogo world is a torus that is the edges of the screen are connected to each other so turtles and patches wrap around Can I use a di
170. ttons create files in plain text comma separated values csv format CSV files can be read by most popular spreadsheet and database programs as well as any text editor BehaviorSpace Guide 86 FAQ Frequently Asked Questions Feedback from users is very valuable to us in designing and improving NetLogo We d like to hear from you Please send comments suggestions and questions to feedback ccl northwestern edu and bug reports to bugs Q2ccl northwestern edu General e What is NetLogo written in e How do cite NetLogo in an academic publication e How do cite a model from the Models Library in an academic publication e What license is NetLogo released under Are there are any legal restrictions on use redistribution etc e Is the source code to NetLogo available e Do you offer any workshops or other training on NetLogo e Has anyone written a model of x e What s the difference between StarLogo MacStarLogo StarLogoT and NetLogo Downloading e The download form doesn t work for me Can I have a direct link to the software e Downloading NetLogo takes too long Can get it some other way like on a CD e downloaded and installed NetLogo but the Models Library has few or no models in it What s going on Usage e How do change how many patches there are e How big can my model be How many turtles patches procedures buttons etc e When will NetLogo be a native app on Mac OS X e Can l import
171. ttons on the Interface Toolbar only the key item is affected The key item is indicated by a darker gray border than the other items Unselecting To unselect all interface elements click the mouse on the white background of the Interface tab To unselect an individual element control click Macintosh or right click other OS the element and choose Unselect from the popup menu Editing To change the characteristics of an interface element select the element then press the Edit button on the Interface Toolbar You may also double click the element once it is selected A third way to edit an element is to control click Macintosh or right click other OS it and choose Edit from the popup menu If you use this last method it is not necessary to select the element first Moving Select the interface element then drag it with your mouse to its new location If you hold down the shift key while dragging the element will move only straight up and down or straight left and right Interface Guide 51 NetLogo 1 1 User Manual Resizing Select the interface element then drag the black handles in the selection border Deleting Select the element or elements you want to delete then press the Delete button on the Interface Toolbar You may also delete an element by control clicking Macintosh or right clicking other OS it and choosing Delete from the popup menu If you use this latter method it is not necessary to select the
172. turtles at turtles here uphill value from Patch related primitives clear patches cp diffuse diffuse4 distance distance nowrap distancexy distancexy nowrap inspect myself neighbors neighbors4 no label nobody nsum nsum4 of patch patch at patch here patches sprout value from Agentset primitives any ask at points BREED at BREED here count histogram in radius max one of min one of neighbors neighbors4 one of other turtles here other BREED here patches random one of turtles with turtles at turtles here values from Color primitives extract hsb extract rgb hsb rgb scale color shade of wrap color Control flow and logic primitives and end if ifelse locals loop not or repeat report semicolon stop startup timer to to report wait while without interruption xor Display primitives clear all ca clear graphics cg clear patches cp clear turtles ct display no display no label screen edge x screen edge y screen size x screen size y Primitives Dictionary 94 NetLogo 1 1 User Manual HubNet primitives hubnet broadcast hubnet fetch message hubnet message hubnet message source hubnet message tag hubnet message waiting hubnet reset hubnet set client interface hubnet set tags Input output primitives clear output export output export plot export world import world print read from string show type user choice user input user message List primitives but first but last empty first fput is list item last length list lout
173. ubnet set tags primitive This will cause an error if no data has been fetched from the server So be sure to fetch the data with hubnet fet ch message before calling this hubnet message This reports the data collected by hubnet fetch message This will cause an error if no data has been fetched from the server So be sure to fetch the data with hubnet fetch message before calling this Sending data It is also possible to send data from NetLogo to the server to be accessed by the calculators Note It is not currently possible to send data from NetLogo directly to only an individual calculator However once the server has the data any connected calculator can grab it This is done using the calculators communication facilities rather than through NetLogo The primitive for sending data to the server is hubnet broadcast variable name value This broadcasts value from NetLogo to the variable variable name on the server You may send a number a string a list of numbers or a matrix a list of lists of numbers The examples of sending the various types of data that you can send are as follows data type number t broadcast A 3 14 string t broadcast STRI I THERE list of numbers hubnet broadcast L2 1 2 3 matrix of numbers hubnet broadcast VENIS TEE P AT Examples Study the models in the HubNet Activities section of the Models Library to see how these primitives are used in pract
174. ue of elevation is NEAR to the highest within about 1 for our values change their color to white and all patches whose values are NEAR to the lowest become black This is so that they ll be easier to see You can make a couple of quick changes here if you wish they won t affect the rest of the model Instead of saying sei pcolor white and set pcolor black you can say set pcolor blue and set pcolor red or whatever other colors you wish Also you can change the range of highest peaks and lowest peaks by changing the number 100 to some other number After this create two monitors in the Interface Window with the Toolbar You make them just like buttons and sliders using the monitor icon on the Toolbar Name one of them highest and one of them lowest Now every time you click setup and redistribute the values of elevation you ll know exactly what the highest values are and where they can be found setup t go Em highest lowest An Uphill Algorithm Okay Finally we re ready to start hill climbing To rehash we ve got some turtles randomly spread out from the origin and we ve got a landscape of patches whose primary attribute is their elevation Lastly we have two kinds of tools to help us understand the patch landscape each patch has a color depending on its value of elevation and we have a pair of monitors telling us what the highest peak and lowest valley are What we need now is for the
175. unity to work out different scenarios or hypotheses Altering the settings and then running the model to see how it reacts to those changes can give you a deeper understanding of the phenomena being modeled Switches and sliders give you access to a model s settings Here are the switches and sliders in Wolf Sheep Predation Tutorial 1 Models 18 NetLogo 1 1 User Manual Grass settings Sheep settings Wolf settings Let s experiment with their effect on the behavior of the model Open Wolf Sheep Predation if it s not open already e Press setup and go and let the model run for about a 100 ticks Note there is a readout of the number of ticks right above the plot e Stop the model by pressing the go button What happened to the sheep over time Let s take a look and see what would happen to the sheep if we change a few settings e Turn the show energy switch on Press setup and let the model run for about the same amount of time as before What did this switch do to the model Was the outcome the same as your previous run e Turn the show energy switch off e Using the same procedure as above try out the grass switch How does this switch affect what happens in the model The switches in Wolf Sheep Predation demonstrate that sometimes a switch or slider only changes how the model looks while sometimes the switch or slider actually changes the behavior of model For example the show ener
176. urtles here with mate nobody if candidate nobody set mate candidate set mate of candidate turtle who turtle who me end Using without interruption ensures that while a turtle is choosing a mate all other agents are frozen This makes it impossible for two turtles to choose the same mate l tried to put at after the name of a variable for example variable at 1 0 but NetLogo won t let me Why not This syntax was supported by StarLogoT and some beta versions of NetLogo but was removed from NetLogo 1 0 Instead for a patch variable write e g pcolor of patch at 1 0 andfora turtle variable write e g color of one of turtles at 1 0 I m getting numbers like 0 10000000004 and 0 799999999999 instead of 0 1 and 0 8 Why FAQ Frequently Asked Questions 92 NetLogo 1 1 User Manual That math operations sometimes produce slightly inaccurate results like these is a limitation of IEEE floating point arithmetic in general NetLogo uses Java to do math and Java implements the IEEE standard But there are some cases where NetLogo should compensate for it and doesn t We fixed a number of them in the betas leading up to 1 0 and a fix for one more appeared in 1 1 namely sliders will no longer occasionally produce such slightly off numbers But in general you shouldn t expect floating point arithmetic to produce absolutely exact answers The precision primitive is handy for rounding off numbers for display purpo
177. ve instructions to hundreds or thousands of independent agents all operating in parallel This makes it possible to explore the connection between the micro level behavior of individuals and the macro level patterns that emerge from the interaction of many individuals NetLogo lets students open simulations and play with them exploring their behavior under various conditions It is also an authoring tool which enables students teachers and curriculum developers to create their own models NetLogo is simple enough that students and teachers can easily run simulations or even build their own And it is advanced enough to serve as a powerful tool for researchers in many fields NetLogo has extensive documentation and tutorials for all of its features It also comes with a Models Library which is a large collection of pre written simulations that can be used and modified These simulations address many content areas in the natural and social sciences including biology and medicine physics and chemistry mathematics and computer science and economics and social psychology Several model based inquiry curricula using NetLogo are currently under development NetLogo can also power a classroom participatory simulation tool called HubNet Through the use of handheld devices such as Texas Instruments TI 83 calculators each student can control an agent in a simulation over a wireless network Note HubNet is not yet released to the general publi
178. w has turned all yellow and the street has disappeared Why didn t the cars turn yellow too Looking back at the command that was written we asked only the patches to change their color In this model the cars are represented by a different kind of agent called turtles Therefore the cars did not received these instructions and thus did not change e Type in the Command Center the text shown below Command Center Clear D gt ask patches set pcolor yellow Was the result what you expected Your Graphics Window should have a yellow background with a line of brown cars in the middle of the window Tutorial 2 Commands 27 NetLogo 1 1 User Manual The NetLogo world is a two dimensional world that is made up of turtles patches and an observer The patches create the ground in which the turtles can move around on and the observer is a being that oversee everything that is going on in the world For a detailed description and specifics about this world refer to the NetLogo Programming Guide In the Command Center we have the ability to give an observer a command turtles a command or patches a command We choose these by using the popup menu located in the bottom left corner of the Command Center You can also use the tab key on your keyboard to choose between them e In the Command Center click on the O gt Command Center D ask patches set pcolor yellow D ask turtles set color brown
179. ward in its current heading These primitives are useful for testing the patch ahead of the turtle before moving if food of patch at dx dy gt 0 fd 1 eat E Primitives Dictionary 107 NetLogo 1 1 User Manual empty empty list empty string Reports true if the given list or string is empty false otherwise Note the empty list is written The empty string is written end end Used to conclude a procedure See to and to report every every number commands Runs the given commands at most every number seconds More technically the behavior of every can described as follows When an agent reaches an every it checks a timer to see if the given amount of time has passed since the last time the same agent ran the commands in the every in the same context If so it runs the commands otherwise they are skipped and execution continues The next time the agent reaches the every the commands will get another chance to run Here in the same context means during the same ask or button press or command typed in the Command Center So it doesn t make sense to write ask turtles every 0 5 because when the ask finishes the turtles will all discard their timers for the every The correct usage is shown below every 0 5 ask turtles fd 1 twice a second the turtles will move forward 1 every 2 set index index 1 every 2 seconds index is incremented See also wait
180. wolves from eat patches own countdown to setup ca set ticks 0 ask patches set pcolor green if grass indicates whether the grass switch is on if it is true then grass grows and the sheep eat it if it false then the sheep don t need to eat ask patches set countdown random grass delay initialize grass grow c if random 2 D half the patches start out with grass set pcolor brown To determine if the code has any errors press the Compile button If there are any syntax errors the Errors Tab will come to the front of the screen and turn red The code that contains the error will be highlighted and a comment will appear in the top box Switching tabs also causes the code to be compiled and any errors will be shown so if you switch tabs pressing the Compile button first isn t necessary Interface Guide 54 NetLogo 1 1 User Manual To find a fragment of code in the procedures click on the magnifying glass on the Procedures Toolbar Then enter the text you are looking for and hit the Find button The Find Again button finds the next location of the word or fragment of code throughout the procedure To find a particular procedure definition in your code use the Procedures popup menu in the Procedures Toolbar The menu lists all procedures in alphabetical order For more information about writing procedures read Tutorial 3 Procedures and the Programming Guide Information Tab The Informa
181. you need help configuring your browser to have the correct proxy settings ask your network administrator We are actively working to remove this restriction on the NetLogo application We also expect that a future version of the TI Navigator system may help address the situation If you have any trouble running HubNet in your classroom please contact us at feedback ccl northwestern edu HubNet Programming Guide This section explains how to use NetLogo to modify the existing HubNet activities or build your own new HubNet activities Calculator The calculator is able to send and receive the following data types from NetLogo e Valid calculator lists such as L1 or PLOTS e Valid calculator matrices such as A or B HubNet Guide 72 NetLogo 1 1 User Manual e Valid calculator strings such as Str1 or Str5 e Numbers such as A or B The calculator sends and receives data by storing a set of parameters in the string Stro Depending upon what type of data you are trying to send or receive StrO will have different values For instance if the modeler wanted to create and send a list of numbers in the list L1 it would be done as follows Set the value of the list to some numbers in this case 20 A and B where A and B are number variables that are set previously in the calculator code Then write 20 A B gt L1 1 L1 gt StroO Asm prgmSENDVAR The length of the list of numbers that a calculator sends depe

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