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java.lang.Objectncsa.hdf.object.HObject
ncsa.hdf.object.Dataset
ncsa.hdf.object.CompoundDS
ncsa.hdf.object.h4.H4Vdata
H4Vdata describes a multi-dimension array of HDF4 vdata, inheriting CompoundDS.
A vdata is like a table that consists of a collection of records whose values are stored in fixed-length fields. All records have the same structure and all values in each field have the same data type. Vdatas are uniquely identified by a name, a class, and a series of individual field names.
How to Select a Subset
Dataset defines APIs for read, write and subet a dataset. No function is defined to select a subset of a data array. The selection is done in an implicit way. Function calls to dimension information such as getSelectedDims() return an array of dimension values, which is a reference to the array in the dataset object. Changes of the array outside the dataset object directly change the values of the array in the dataset object. It is like pointers in C.
The following is an example of how to make a subset. In the example, the dataset
is a 4-dimension with size of [200][100][50][10], i.e.
dims[0]=200; dims[1]=100; dims[2]=50; dims[3]=10;
We want to select every other data points in dims[1] and dims[2]
int rank = dataset.getRank(); // number of dimension of the dataset long[] dims = dataset.getDims(); // the dimension sizes of the dataset long[] selected = dataset.getSelectedDims(); // the selected size of the dataet long[] start = dataset.getStartDims(); // the off set of the selection long[] stride = dataset.getStride(); // the stride of the dataset int[] selectedIndex = dataset.getSelectedIndex(); // the selected dimensions for display // select dim1 and dim2 as 2D data for display,and slice through dim0 selectedIndex[0] = 1; selectedIndex[1] = 2; selectedIndex[1] = 0; // reset the selection arrays for (int i=0; i
- See Also:
- Serialized Form
Field Summary
Fields inherited from class ncsa.hdf.object.CompoundDS isMemberSelected, memberDims, memberNames, memberOrders, memberTypes, numberOfMembers
Fields inherited from class ncsa.hdf.object.Dataset chunkSize, compression, data, datatype, dimNames, dims, H5Z_FILTER_CONFIG_DECODE_ENABLED, H5Z_FILTER_CONFIG_ENCODE_ENABLED, rank, selectedDims, selectedIndex, selectedStride, startDims
Fields inherited from class ncsa.hdf.object.HObject hasAttribute, oid, separator
Constructor Summary H4Vdata(FileFormat fileFormat, java.lang.String name, java.lang.String path)
H4Vdata(FileFormat fileFormat, java.lang.String name, java.lang.String path, long[] oid)
Creates an H4Vdata object with specific name and path.
Method Summary void
close(int vsid)
Closes access to this object.Dataset
copy(Group pgroup, java.lang.String dname, long[] dims, java.lang.Object data)
Copy this dataset to another group.Datatype
getDatatype()
returns the datatype of this dataset.int
getFieldCount()
Returns the number of fields.int[]
getFieldOrders()
Returns the orders of fieldsjava.util.List
getMetadata()
Loads the metadata such as attributes and type of the the data object into memory if the metadata is not loaded.int
getRecordCount()
Returns the number of records.void
init()
Initializes the H4Vdata such as dimension sizes of this dataset.int
open()
Opens access to this object.java.lang.Object
read()
Loads and returns the data value from file.byte[]
readBytes()
Read data values of this dataset into byte array.void
removeMetadata(java.lang.Object info)
Deletes an existing metadata from this data object.void
write(java.lang.Object buf)
Write data values into file.void
writeMetadata(java.lang.Object info)
Saves a specific metadata into file.
Methods inherited from class ncsa.hdf.object.CompoundDS getMemberCount, getMemberNames, getMemberOrders, getMemberTypes, getMemeberDims, getSelectedMemberCount, getSelectedMemberOrders, isMemberSelected, selectMember, setMemberSelection
Methods inherited from class ncsa.hdf.object.Dataset byteToString, clearData, convertFromUnsignedC, convertToUnsignedC, getChunkSize, getCompression, getData, getDimNames, getDims, getHeight, getRank, getSelectedDims, getSelectedIndex, getStartDims, getStride, getWidth, setData, stringToByte, write
Methods inherited from class ncsa.hdf.object.HObject equalsOID, getFID, getFile, getFileFormat, getName, getOID, getPath, hasAttribute, setName, setPath, toString
Methods inherited from class java.lang.Object clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Constructor Detail H4Vdata
public H4Vdata(FileFormat fileFormat, java.lang.String name, java.lang.String path)
H4Vdata
public H4Vdata(FileFormat fileFormat, java.lang.String name, java.lang.String path, long[] oid)
- Creates an H4Vdata object with specific name and path.
- Parameters:
fileFormat
- the HDF file.name
- the name of this H4Vdata.path
- the full path of this H4Vdata.oid
- the unique identifier of this data object.
Method Detail getDatatype
public Datatype getDatatype()
- Description copied from class:
Dataset
- returns the datatype of this dataset.
- Specified by:
getDatatype
in classDataset
copy
public Dataset copy(Group pgroup, java.lang.String dname, long[] dims, java.lang.Object data) throws java.lang.Exception
- Description copied from class:
Dataset
- Copy this dataset to another group.
- Specified by:
copy
in classDataset
- Parameters:
pgroup
- the group which the dataset is copied to.dname
- the name of the new dataset.dims
- the dimension sizes of the the new dataset.data
- the data to be copied.- Returns:
- the new dataset.
- Throws:
java.lang.Exception
readBytes
public byte[] readBytes() throws HDFException
- Description copied from class:
Dataset
- Read data values of this dataset into byte array. readBytes() loads data as arry of bytes instead of array of its datatype. For example, for an one-dimension 32-bit integer dataset of size 5, the readBytes() returns of a byte array of size 20 instead of a int array of 5.
readBytes() is most used for copy data values, at which case, data do not need to be changed or displayed.
- Specified by:
readBytes
in classDataset
- Throws:
HDFException
read
public java.lang.Object read() throws HDFException
- Description copied from class:
Dataset
- Loads and returns the data value from file.
- Specified by:
read
in classDataset
- Throws:
HDFException
write
public void write(java.lang.Object buf) throws HDFException
- Description copied from class:
Dataset
- Write data values into file.
- Specified by:
write
in classDataset
- Parameters:
buf
- the data to write- Throws:
HDFException
getMetadata
public java.util.List getMetadata() throws HDFException
- Description copied from interface:
DataFormat
- Loads the metadata such as attributes and type of the the data object into memory if the metadata is not loaded. If the metadata is loaded, it returns the metadata. The metadata is stored as a collection of metadata ojbects in a List.
- Returns:
- the list of metadata objects.
- Throws:
HDFException
- See Also:
List
writeMetadata
public void writeMetadata(java.lang.Object info) throws java.lang.Exception
- Description copied from interface:
DataFormat
- Saves a specific metadata into file. If the metadata exists, it updates its value. If the metadata does not exists, it creates and attach the new metadata to the object and saves it into file.
- Parameters:
info
- the specific metadata.- Throws:
java.lang.Exception
removeMetadata
public void removeMetadata(java.lang.Object info) throws HDFException
- Description copied from interface:
DataFormat
- Deletes an existing metadata from this data object.
- Parameters:
info
- the metadata to delete.- Throws:
HDFException
open
public int open()
- Description copied from class:
HObject
- Opens access to this object.
Sub-classes have to implement this interface so that different data objects have their own ways of how the data resources are opened.
- Specified by:
open
in classHObject
- Returns:
- the interface identifier for access this object.
close
public void close(int vsid)
- Description copied from class:
HObject
- Closes access to this object.
- Specified by:
close
in classHObject
- Parameters:
vsid
- the object identifier. Sub-classes have to implement this interface so that different data objects have their own ways of how the data resources are closed.
init
public void init()
- Initializes the H4Vdata such as dimension sizes of this dataset.
- Specified by:
init
in classDataset
getRecordCount
public int getRecordCount()
- Returns the number of records.
getFieldCount
public int getFieldCount()
- Returns the number of fields.
getFieldOrders
public int[] getFieldOrders()
- Returns the orders of fields
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