MetApps Data System Developers Manual
Contents
1. write some data try n ncfile write temperature origin data catch IOException e System err println ERROR writing file throw e all done ncfile close 1 7 ucar nc2 dods DODSNetcdfFile It is possible to open and manipulate a read only file on a DODS server by instantiating a DODSNetcdfFile whichis a subclass of NetcdfFile and so inherits the same API public class ucar nc2 dods DODSNetcdfFile extends NetcdfFile public DODSNetcdfFile String url throws IOException DODSException MalformedURLException For example NetcdfFile ncfile try ncfile new DODSNetcdfFile dods motherlode ucar edu cgi bin dods nph nc dods model 2001012200 eta nc catch dods dap DODSException e System out println DODS error e catch java net MalformedURLException e System out println bad URL error te j catch IOException e System out println IO error e Note that this uses the protocol dods instead of http in order to distinguish other possible protocols that also use http If you use http it will be converted to dods and returned in this canonical form in the getName method 2 Multidimensional Arrays The ucar ma2 package is independent of the ucar nc2 package and is intended for general multidimensional array use Its design is motivated by the needs for NetCDF data to be handled in a2. sum iter getDoubleNext Note that in the above example A can be of arbitrary rank public interface IndexIterator public boolean hasNext for each data type public double getDoubleNext public double getDoubleCurrent public void setDoubleNext double val public void setDoubleCurrent double val There are two special kinds of iterators Array get IndexIteratorFast returns an Iterator that iterates over the array in an arbitrary order It can be used to make iteration as fast as possible when the order of the returned elements is immaterial for example in the summing example above Array getRangeIterator returns a range iterator that iterates over a subset of an array in logical order This is an alternative and equivalent to first creating an array section and then obtaining an Iterator In the following example the sum is made only over the first 10 rows and all columns of the array int sum 0 IndexIterator iter A getRangeIterator new Ranges 2 new Range 0 9 null while iter hasNext sum iter getIntNext 2 5 Array Implementation ArrayAbstract is the superclass for our implementations of Array which use Java 1 D arrays for the data storage There is a concrete class that extends ArrayAbstract for each data type e g ArrayDouble For each data type there is a concrete subclass for each rank 0 7 for example ArrayDouble D3 is a concrete class s
3. public static ArrayAbstract factory java lang Object javaArray Note that in this case the data elements are copied out of the Java array into the private ArrayAbstract storage IndexImpl is a concrete general rank implementation of Index and is extended by rank specific subclasses for efficiency we have rank 0 7 implementations ArrayAbstract and its subclasses have an IndexImp1 of the appropriate rank that is delegated all rank specific functions This orthogonal design keeps the number of classes small and makes adding new ranks or data types quite simple The logical view operations flip section transpose slice and permute are implemented by manipulating the index calculation within the IndexImp1 object These operations are affine as is the operation that transforms the n dim index into the 1 dim element index and therefore any composition is an affine transformation The resulting transformation is immutable and can be computed during the IndexImp1 object construction Therefore there is no extra cost associated with the index calculation for these operations or any composition of them during element access These operations do logical data reordering physical reordering can be done by making an array copy An IndexIterator traverses array elements in logical order which we have defined as row major as in C An iterator can in principle be more efficient than other element accesses because 1 the index values cannot
4. Integer or Short public class Attribute public String getName public Class getValueType String or subclass of Number public boolean isString public boolean isArray public int getLength 1 for scalars public Object getValue public String getStringValue public Number getNumericValue public Number getNumericValue int elem 1 3 ucar nc2 Variable A Variable is a multidimensional array stored in a local file or remote network device a scalar variable is a rank 0 array It has a name and a collection of dimensions and attributes as well as logically containing the data itself The dimensions are returned in getDimensions in order of most slowly varying first leftmost index for Java and C programmers The underlying array elements are always primitives and may have Class types of double class float class int class short class byte class or char class Note the absence of the long and boolean types these are not supported in the underlying file format Data access is handled by calling read which returns the data in a memory resident Array object This Array has the same element type as the variable and the requested shape A subsection is specified using the origin and shape parameters which for each dimension must satisfy origin ii shape ii lt Variable shape ii public class Variable implements ucar ma2 IOArray public String getName public int getRan
5. filename or URL pathname public Iterator getVariableIterator get list of Variables public Variable findVariable String varName find specific Variable public Iterator getDimensionIterator get list of Dimensions public Dimension findDimension String dimName get specific Dimension public Iterator getGlobalAttributeIterator get list of global Attributes public Attribute findGlobalAttribute String attName specific Attribute public Attribute findGlobalAttributeIgnoreCase String attName public String findAttValuelIgnoreCase Variable v String attName String defValue The NetcdfFile String filename constructor accesses local files while the NetcdfFile URL url constructor uses the HTTP 1 1 protocol to access netCDF files that are stored on web servers The URL should begin with http for example http www unidata ucar edu staff caron test mydata nc The efficiency of the remote access depends on how the data is accessed Reading large contiguous regions of the file should generally be good while skipping around the file and reading small amounts of data will be poor In that case you would be better copying the file to a local drive or putting the file into a DODS server The findAttValueIgnoreCase is a convenience method for St ring valued attributes which returns the specified default value de fValue if the attribute name is not found in the file Specifying a null for the variable means to sear
6. general arbitrary rank type independent way and also by the requirements of the JavaGrande numeric working group 3 It is often critically important for performance that the movement of data between memory and disk is carefully managed The data in a NetCDF file for example is stored out of memory on a local or network file and the NetCDF library allows efficient extraction of data subsets At the same time it is sometimes a useful abstraction to handle data in a general way independent of storage location A ucar ma2 Array object has its data in the computer s main memory and so is said to be memory resident A ucar ma2 IOArray object has its data stored on an I O device such as a disk file ucar ma2 MultiArray is the superclass of both for location independent manipulation Note that to actually get at the data of aMultiArray object you must explicitly call read to bring the data into memory An IOArray will actually do the read while an Array object will just return itself The fact that an TOArray can throw an IOException but an Array object cannot may in fact be a critical factor in how these objects are used 4 Similarly some applications may need to know whether the IOException is from a local or remote file In this case you should test if the IOException is an instance of java rmi RemoteException The following is an overview of the important public interfaces of the ucar ma2 classes Consult the javadoc f
7. Bo seds eta EL BNN NN 11 EXAMPLE 2 PRINT ALL THE DATA IN A NETCDF FILE cccccesssssssssssssssssssssesssesssssesesesesssssssssesesesssesesseees 14 REFERENGES ta BEAN Bentak REK RBUN BS an ENAM asa ba 16 Introduction This is user documentation for the ucar nc2 ucar nc2 dods and ucar ma2 java packages also known as NetCDF Java version 2 and MultiArray verion 2 packages These are a separate and logically unrelated Application Programmer s Interface API from Unidata s earlier ucar netcdf and ucar multiarray packages 1 All of these packages are freely available and the source code is released under the Lesser GNU Public License LGPL 2 The ucar nc2 package is intended to be a straightforward Java interface to NetCDF files It is built on the ucar ma2 package which is an abstraction for multidimensional arrays of primitive types 3 1 NetCDF A NetCDF file is a collection of dimensions attributes and variables A dimension is a named array index An attribute is a key value pair A variable is a multidimensional array backed by an I O device A variable also has a name and a collection of dimensions and attributes Net cdfFile is used for read only NetCDF files while NetcdfFilewriteable allows writing and a DODSNetcdfFile allows read only access to DODS files through the NetCDF API Note there are no public constructors for Dimension Attribute Or Variable the only way to create these is through NetcdfFil
8. IOException e System err println ERROR writing file all done try ncfile close 13 catch IOException e System err println ERROR writing file Example 2 Print all the data in a netCDF file import ucar ma2 import ucar nc2 import java io IOException import java util Iterator Simple example to print contents of an existing netCDF file of unknown structure much like ncdump A difference is the nesting of multidimensional array data is represented by nested brackets so the output is not legal CDL that can be used as input for ncgen Je EP public class DumpNetcdf public static void main String args if args length 1 new DumpNetcdf args 0 else new DumpNetcdf example nc public DumpNetcdf String fileName try NetcdfFile nc new NetcdfFile fileName open it readonly System out println nc output schema in CDL form like ncdump System out println data Iterator vi nc getVariableIterator while vi hasNext Variable v Variable vi next Array varMa v read System out print v getName System out println ArrayToString varMa catch java io I0Exception e e printStackTrace public String ArrayToString Array ma StringBuffer buf new StringBuffer ArrayToStringHelper ma new IndentLevel return buf toString Maintains ind
9. be out of range and therefore do not need to be bounds checked and 2 the element calculation usually changes by a fixed stride each time We take advantage of these facts in our implementation as well as package private accessor methods to reduce the number of method calls per data access from 3 to 2 Examples Example 1 Create a netCDF File import ucar ma2 import ucar nc2 import java io IOException Simpl xample to create a new netCDF file corresponding to the following CDL netcdf example dimensions lat 3 lon 4 time UNLIMITED variables int rh time lat lon rh long name relative humidity rh units percent double T time lat lon T long name surface temperature FF PPP RKA oo F OF T units degC float lat lat lat units degrees north float lon lon lon units degrees east int time time time units hours 11 global attributes x title Example Data data rh amp 1 2 3 4 i 5 6 7 8 x Or AOR Ita LZ 214 227 235 24 25 26 21 28 X 297 30y B17 32 3 TR x Lp 2 85 4y 2 Ay 60y By 3 6 9 12 x 25 94 97 hoe LO x 53 LO 154 204 Penny L5G 222572 30 F lat 41 40 39 lon 109 107 105 103 time 6 18 oH al RS public class CreateNetcdf static String fileName example nc public void main String arg NetcdfFileWriteable ncfile ne
10. the number of dimensions and get Size returns the total number of elements in the Array The getElementType method returns the data type of the backing store e g double class float class etc Data element access is described in the sections following this one Logical views of the array are created in several ways The section method creates a subarray of the original array The slice method is a convenience routine for the common section operation of rank 1 section of the array The transpose method transposes two dimensions while permute is a general permutation of the indices The flip method flips the index of the specified dimension so that it logically runs from n 1 to 0 instead of from 0 to n 1 The reduce method allows user control over rank reduction All of these logically reorder or subset the data without copying Methods that create new Arrays by copying the data are copy sectionCopy and reshape The data can be copied into a Java array using the copyTolDjavaArray and copyToNDjavaArray methods In the first case a 1D Java array of the appropriate primitive type is created and the data is copied to it in logical order rightmost indices varying fastest In the second case an N dimensional Java array is created that matches the Array shape and the data is copied into it The user must cast the returned Object to the appropriate Java array type 2 3 ucar ma2 Index Accesses to
11. NetCDF Java version 2 User s Manual John Caron Apr 26 2001 INTRODUCTION scsccsssscssossesessesevensvensececs sosenssusvesccevesasossucnncceseesdessuseeoeseesedesuvedovsusecsesedsssoesvenesdessceseveeeesedvesse 1 TONED CD Bibie SIS in BSN NN 1 I 1 UCAR NE2 DIMENSION 22001222 ELANG NN NS SNN NN 2 1220 CAR NE2ATIRIBU TE ba EE E ANE SATA uu na 2 1 3 UCAR NECX VARIABLE saii Te ESA BER n RE ESE AAN A AEE A AAE E 2 14 UCAR NC2 VARIABLES TANDARDIZED 5s renie o E e e E a o o 3 T5 UCARNGZNETOD a S TB cscs bcc AE EEE EE E E E E E E E EE E AEE OE EE 4 1 6 UCAR NE2 NETEDFEFILEW RITEABIE minii e SENIN BEN a E NE A R EEEa 4 TT UCAR NC DOODS DODSNETCDEFILE s iieii ee e a R A dei exe RAN E ies RE uu 6 2 MULTIDIMENSIONAL ARRAYG csssccscssssscesssccccssnccecssccccessscccessneccsessncecscacecessnaccsessseecessaccessnees 6 2 1 UCAR MA2 MULTIARRAY AND UCAR MA2 IOARRAY oom enakan 7 2 2 UCAR MA2 ARRAY IN MEMORY MULTIDIMENSIONAL ARRAYS OF PRIMITIVES oooooo o ooooo 7 IAE VICAR IMAZ INDEX ORE La Bus ae bbe didi hE 9 2 4 UCAR MA2 INDEXITERATOR ccccsssccccecsesessscesececeesesscaeseecceceesaseceeececeeaueeeeececeeseasseeeecesesesaaeeeeseeesensaaes 9 2 5 ARRAY IMPLEMENTATION csecssccsccecsesssececececcessseseeececeessaeseseescseseseseeeecceeseaaeeeesesesesnsaeeeeeeseeennaaeas 10 EXAMPLES benni benni coscsesdeacsaveveseassesona cheeses snsckeussdeesosessocsdacese soosoosiaaseeevesodsoeseccessseesse sucseoveeccnse 11 EXAMPLE I GREATE A NETCD BRI
12. be of type Float Double public void addVariableAttribute S value must be 1D array of double float public void addVariableAttribute S 11 public void create finish structure definition create file throws IOException write data to file public boolean write String varName TOException int public void close throws IOException Class varType tring varName String attName String value Integer tring varName String attName Number value origin int short char byte Object arrayValue Dimension varShape Short or Byte int short char byte tring varName String attName Object value ArrayAbstract data throws As an example to create a new file the program might look like NetcdfFileWriteable ncfile new NetcdfFileWriteable Ncfile setName data mydata nc define dimensions Dimension latDim ncfile addDimension lat 64 Dimension lonDim ncfile addDimension lon 128 define Variables Dimension dims new Dimension 2 dims 0 latDim dims 1 lonDim ncfile addVariable temperature double class dims ncfile addVariableAttribute temperature units K add global attribute ncfile addGlobalAttribute version new Double 1 2 create the file try ncfile create catch IOException e System err println ERROR creating file throw e
13. ch global attributes otherwise search for the attribute in the given variable 1 6 ucar nc2 NetcdfFileWriteable ANetcdfFileWriteable allows a NetCDF file to be created or written to Note this can only be done with local not remote files Because of the limitations of the underlying implementation a NetCDF file can only have dimensions attributes and variables added to it at creation time Thus when a file is first opened it in is define mode where these may added Once create is called the dataset structure is immutable After create has been called you can then write the data values See following example public class NetcdfFileWriteabl xtends NetcdfFile create new file public NetcdfFileWriteable public void setName String filename open existing file for writing data only public NetcdfFilewriteable String filename 11 pub add Tic new Dimension Dimension addDimension String dimName add new global Attributes public void addGlobalAttribute String attName value must be of type Float Double public void addGlobalAttribute String attName Integer throws IOException int dimLength String value Short or Byte Number value value must be 1D array of double float public void addGlobalAttribute String attName add new Variable and variable Attribu public void addVariable String varName public void addVariableAttribute S Les value must
14. e addGlobalAttribute title Example Data create the file try ncfile create catch IOException e System err println ERROR creating file assert false System out println ncfile ncfile write the RH data one value at a time to an Array int rhData 1 2 3 4 5 6 7 8 9 10 11 12 21 227p 237 24a 25 267 29 28 5 2 9 30 S31 S23 443 ArrayInt rhA new ArrayInt D3 2 latDim getLength lonDim getLength int i j k Index ima rhA getIndex write for i 0 i lt 2 i for j 0 j lt latDim getLength j for k 0 k lt lonDim getLength k rhA setInt ima set i j k rhData i j k write rhData out to disk try ncfile write rh rhA catch IOException e System err println ERROR writing file Here s an ArrayAbstract approach to set the values of T all at once double J tData 1 2 3 4 2 4 6 8 3 6 9 12 2 5 S7 Tes DO top TOR La 20 AA on lo 22 57 3077 hi try ncfile write T ArrayAbstract factory tData catch IOException e System err println ERROR writing file Store the rest of variable values try ncfile write lat ArrayAbstract factory new float 41 40 39 ncfile write lon ArrayAbstract factory new float 109 107 105 103 ncfile write time ArrayAbstract factory new int 6 18 catch
15. entation level for printing nested structures static class IndentLevel 14 private int level 0 private int indentation private StringBuffer indent private StringBuffer blanks public IndentLevel this 4 public IndentLevel int indentation if indentation gt 0 this indentation indent new StringBuffer blanks new StringBuffer for int i 0 i lt indentation blanks append public void incr level indentation indent append blanks public void decr level indentation indentation indent setLength level public String getIndent return indent toString i private String ArrayToStringHelper Array ma final int rank Index ima ma ma getRank tIndex if rank 0 g return ma getObject ima toString StringBuffer bu f new StringBuffer buf append n ilev getIndent ilev incr final int dims ma getShape final int last for int ii 0 Array slice dims 0 ii lt last ma slice 0 ii ii TEEN jasa buf append ArrayToStringHelper slice il if ii last 1 buf append ilev decr if rank gt 1 buf append n ilev getIndent buf append return buf toString IndentLevel ilev 15 References 1 Davis G P and D F Fulker 1999 Extending t
16. ewriteable The semantics of NetCDF files are slightly different through this Java API than through the C C or Fortran APIs that you may be used to A NetCDF file can only have Dimension Attribute and Variable objects added to it at creation time Thus it is not possible to put a file into define mode to add new variables dimensions or attributes or to change the value of an attribute after the file has been created However you can change data values or append new data to existing variables after creation time The following is an overview of the important public interfaces of the ucar nc2 classes Consult the javadoc for more complete and recent details 1 1 ucar nc2 Dimension A Dimension object contains a name and a length If the Dimension is unlimited then the length can increase otherwise it is immutable The method getCoordinateVariable returns the associated coordinate variable or null if none exists A coordinate variable is defined as a Variable with the same name as the Dimension whose single dimension is the Dimension for example float lat lat public class Dimension public String getName public int getLength public boolean isUnlimited public Variable getCoordinateVariable null if none 1 2 ucar nc2 Attribute An attribute is a name value pair where name is a String and value is a String Number or Number Valid subclasses of Number in this context are Byte Double Float
17. g will return true To test if a specific value is missing call isMissing public class VariableStandardized extends Variable public VariableStandardized Variable orgVar public VariableStandardized Variable orgVar boolean useNaNs public boolean hasMissing public boolean isMissing double val There is a lower level interface if you need to distinguish between _ FillValue missing value and valid range attributes see the javadoc for details By default hasMissing is true if any of these attributes are used You can modify this behavior in the constructor or by calling setInvalidDataIsMissing setFillDatalsMissing or setMissingValuelsMissing Data values of float or double NaN are considered missing data and will return true if called with isMissing However hasMissing will not detect if you are setting NaNs yourself If you do not need to distinguish between _ FillValue missing_value and invalid then set useNaNs true in the constructor When the Variable element type is float or double or is set to double because its packed then this sets isMissing data values to NaNs which makes further comparisions more efficient 1 5 ucar nc2 NetcdfFile A NetcdfFile is an immutable read only collection of dimensions attributes and variables public class NetcdfFile public NetcdfFile String filename throws IOException public NetcdfFile URL url throws IOException public String getName
18. he NetCDF Model to Java AMS IIPS Conference January 1999 http www unidata ucar edu packages netcdf java ams99 html 21 http www gnu org copyleft lesser html 3 John Caron Unidata s Design for Multidimensional Arrays in Java ACM Java Grande 2000 Conference June 2000 http www unidata ucar edu staff caron ma2 JavaGrande2000 htm 4 Jim Waldo Geoff Wyant Ann Wollrath and Sam Kendall A Note on Distributed Computing Sun Microsystems Technical Note TR 94 29 1994 http Wwww sun com tech techrep 1994 abstract 29 html 16
19. k rank of the array public int getShape shape of the array public long getSize total number of elements public Class getElementType type of the array elements public boolean isUnlimited iff a Dimension isUnlimited public boolean isCoordinateVariable public ArrayList getDimensions get all Dimensions public Dimension getDimension int i get the ith Dimension public Iterator getAttributeIterator get all Attributes public Attribute findAttribute String attName public Attribute findAttributelgnoreCase String attName read into memory resident Array public Array read throws IOException read all data public Array read int origin int shape throws IOException InvalidRangeException 1 4 ucar nc2 VariableStandardized A VariableStandardized isa subclass of Variable which implements packed data using scale factor and add offset attributes and invalid data using valid min valid max valid range missing dataor FillValue attributes To use you simply pass the original Variable into the VariableStandardized constructor an example of the Decorator design pattern If the Variable has the scale factor and or add_offset attributes the data will automatically be converted to type double or float and computed using the formula new value scale factor old value add offset If the Variable has any of the invalid or missing data attributes hasMissin
20. lic Class getElementType data type of backing array accessor helpers public Index getindex random access public IndexIterator getIndexIterator sequential access public IndexIterator getRangeIterator Range ranges access subset public IndexIterator getIndexIteratorFast arbitrary order accessors for each data type double float long int short byte char boolean there are methods of the form eg public double getDouble Index ima public void setDouble Index ima double value create new Array no data copy public Array flip int dim invert dimension public Array permute int dims permute dimensions public Array reduce rank reduction for any dims of length 1 public Array reduce int dim rank reduction for named dimension public Array section Range ranges create logical subset public Array slice int dim int val rank 1 subset public Array transpose int diml int dim2 transpose dimensions create new Array with data copy public Array copy public Array sectionCopy Range ranges subset public Array reshape int shape total elements must be the same conversion to Java arrays public java lang Object copyTolDJavaArray public java lang Object copyToNDJavaArray The get Shape method returns an integer array containing the length of the Array in each dimension The get Rank method returns
21. methods are identical and so IOArray is actually empty public interface IOArray extends MultiArray 2 2 ucar ma2 Array in memory multidimensional arrays of primitives Array is the abstraction for multidimensional arrays of primitives with data stored in memory Arrays can have arbitrary rank and there are concrete implementations for arrays of rank 0 7 for efficiency The underlying storage can use any of the Java primitive types double float long int short byte char boolean The data can be accessed in a type independent way for example getDouble can be called on an Array of any numeric type The implementing class casts the data to the requested type and throws a runtime ForbiddenConversionException ifthe cast is illegal or uses a direct assign when the requested type is the same as the data type The data type rank and shape of an array are immutable while the data values themselves are mutable Generally this makes Arrays thread safe and no synchronization is done in the Array package There is the possibility of non atomic read writes on 64 bit primitives long double In this case the user should add their own synchronization if needed Presumably 64 bit CPUs will make those operations atomic also public interface Array extends MultiArray array shape and type public long getSize total elements public int getRank array rank public int getShape array dimension sizes pub
22. or more complete and recent details 2 1 ucar ma2 MultiArray and ucar ma2 lOArray A MultiArray has a shape describing its size in each dimension and an element type which is one of the primitive types double class float class long class int class short class byte class boolean class or char class Note that this includes all of the Java primitives even though a ucar nc2 Variable has a restricted subset All of the complicated manipulation of data happens on the memory resident Array object obtained from the read The one exception is that a MultiArray can be sliced by fixing one of the dimensions at a particular value The new MultiArray thus has rank one less than the original This common operation creates a new logical Mult iArray in which no data is moved until a read public interface MultiArray array shape and type public long getSize total elements public int getRank array rank public int getShape array dimension sizes public Class getElementType data type of backing array data access public Array read throws IOException public Array read int origin int shape throws IOException InvalidRangeException Create new MultiArray with logical data reordering public MultiArray sliceMA int which dim int index value An I0Array isa subclass of MultiArray Since the read method signatures in MultiArray must show all subclass exceptions the
23. pecialized for double arrays of rank 3 These rank specific classes are static inner classes of their superclass This design allows handling arrays completely generally through the Array interface in a rank independent way though the Array lt Type gt classes or in a rank and type specific way for ranks 0 7 through the Array lt Type gt D lt rank gt classes The most general way to create an Array is to use the static factory method in ArrayAbstract public abstract class ArrayAbstract implements Array Cloneable static public ArrayAbstract factory Class type int shape The type specific subclasses can be instantiated directly with an arbitrary rank These also add type specific get set accessors for example public class ArrayDouble extends ArrayAbstract constructor public ArrayDouble int dimensions type specific accessors public double get Index i public void set Index i double value If you create your own Array objects you should usually use the rank and type specific subclasses which will provide the most efficient access These classes also add rank specific get set routines for example public static class D3 extends ArrayDouble constructor public D3 int len0 int lenl int len2 type and rank specific accessors public double get int i int j int k public void set int i int j int k double value 10 You may also create an Array from an N dimensional Java array
24. specific array elements are made using an Index object for example double sum 0 0 Index index A getIndex int shape A getShape for i 0 i lt shape 0 i for j 0 j lt shape 1 j for k 0 k lt shape 2 k sum A getDouble index set i j k Note that in this example A can be of any type convertible to a double Index has various convenience methods for setting the element index public interface Index general public Index set int index public void setDim int dim int value convenience methods for rank 0 7 public Index set int v0 set index 0 public Index set int v0 int vl set index 0 1 public Index set int v0 int vl int v2 set index 0 1 2 up to dimension 7 public Index setO int v set index 0 public Index setl int v set index 1 public Index set2 int v set index 2 up to dimension 7 Because an Index object stores state threads that share an Array object must obtain their own Index from the Array 2 4 ucar ma2 Indexlterator An IndexIterator is used to sequentially traverse all data in an Array in logical row major order For example logical order for A i j k has k varying fastest then j then i Note that because of the possibility that A is a flipped or permuted view logical order may not be the same as physical order Example double sum 0 0 IndexIterator iter A getIndexIterator while iter hasNext
25. w NetcdfFileWriteable ncfile setName fileName define dimensions Dimension latDim ncfile addDimension lat 3 Dimension lonDim ncfile addDimension lon 4 Dimension timeDim ncfile addDimension time 1 define Variables Dimension dim3 new Dimension 3 dim3 0 timeDim dim3 1 latDim dim3 2 lonDim int rh time lat lon r rh long_name relative humidity rh units percent ncfile addVariable rh int class dim3 ncfile addVariableAttribute rh long name relative humidity ncfile addVariableAttribute rh units percent double T time lat lon T long name surface temperature T units degC ncfile addVariable T double class dim3 ncfile addVariableAttribute T long name surface temperature ncfile addVariableAttribute T units degC float lat lat lat units ncfile addVariable lat ncfile addVariableAttribute lat 11 float lon lon lon units ncfile addVariable lon degrees north float class new Dimension latDim units degrees north degrees east float class new Dimension lonDim 12 ncfile addVariableAttribute lon units degrees east int time time time units hours ncfile addVariable time int class new Dimension timeDim ncfile addVariableAttribute time units hours title Example Data ncfil
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