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Harris Geospatial / Docs Center / IDL Reference / I/O - HDF / HDF_SD_CREATE

HDF_SD_CREATE

HDF_SD_CREATE

The HDF_SD_CREATE function creates and defines a Scientific Dataset (SD) for an HDF file. Keywords can be set to specify the data type. If no keywords are present a floating-point dataset is created.

Examples


; Create a new HDF file:
SDinterface_id = HDF_SD_START('test.hdf', /CREATE)
; Create an dataset that includes an unlimited dimension:
SDdataset_id = HDF_SD_CREATE(SDinterface_id, 'var1', [9,40,0], /SHORT)

The example for HDF_SD_ATTRSET also demonstrates the use of this routine.

Syntax


Result = HDF_SD_CREATE( SDinterface_id, Name, Dims [, /BYTE] [, /DFNT_CHAR8] [, /DFNT_FLOAT32] [, /DFNT_FLOAT64] [, /DFNT_INT8] [, /DFNT_INT16] [, /DFNT_INT32] [, /DFNT_UINT8] [, /DFNT_UINT16] [, /DFNT_UINT32] [, /DOUBLE] [, /FLOAT] [, HDF_TYPE=type] [, /INT] [, /LONG] [, /SHORT] [, /STRING] )

Return Value


The returned value of this function is the SDS ID of the newly-created dataset.

Arguments


SDinterface_id

An SD ID as returned by HDF_SD_START.

Name

A string containing the name of the variable to be created.

Dims

A 1-based vector specifying the dimensions of the variable. If an UNLIMITED dimension is desired, set the last vector element to zero or a negative number.

Keywords


BYTE

Set this keyword to indicate that the dataset is composed of bytes. Data will be stored with the HDF DFNT_UINT8 data type. Setting this keyword is the same as setting the DFNT_UINT8 keyword.

DFNT_CHAR8

Set this keyword to create a data set of HDF type DFNT_CHAR8. Setting this keyword is the same as setting the STRING keyword.

DFNT_FLOAT32

Set this keyword to create a data set of HDF type DFNT_FLOAT32. Setting this keyword is the same as setting the FLOAT keyword.

DFNT_FLOAT64

Set this keyword to create a data set of HDF type DFNT_FLOAT64. Setting this keyword is the same as setting the DOUBLE keyword.

DFNT_INT8

Set this keyword to create a data set of HDF type DFNT_INT8.

Note: IDL does not have a signed 8-bit integer type. When writing the data to the file using DFNT_INT8, byte values from 0-127 will be written unchaged, while byte values from 128-255 will be wrapped into the range -127 to -1. When reading data of type DFNT_INT8 from the file into IDL, values from 0-127 will be read in unchanged, while values from -127 to -1 will be wrapped into the byte range 128 to 255.

DFNT_INT16

Set this keyword to create a data set of HDF type DFNT_INT16. Setting this keyword is the same as setting either the INT keyword or the SHORT keyword.

DFNT_INT32

Set this keyword to create a data set of HDF type DFNT_INT32. Setting this keyword is the same as setting the LONG keyword.

DFNT_UINT8

Set this keyword to create a data set of HDF type DFNT_UINT8. Setting this keyword is the same as setting the BYTE keyword.

DFNT_UINT16

Set this keyword to create a data set of HDF type DFNT_UINT16.

DFNT_UINT32

Set this keyword to create a data set of HDF type DFNT_UINT32.

DOUBLE

Set this keyword to indicate that the dataset is composed of double-precision floating-point values. Data will be stored with the HDF DFNT_FLOAT64 data type. Setting this keyword is the same as setting the DFNT_FLOAT64 keyword.

FLOAT

Set this keyword to indicate that the dataset is composed of single-precision floating-point values. Data will be stored with the HDF DFNT_FLOAT32 data type. Setting this keyword is the same as setting the DFNT_FLOAT32 keyword.

HDF_TYPE

Set this keyword to the type of data set to create. Valid values are: DFNT_CHAR8, DFNT_FLOAT32, DFNT_FLOAT64, DFNT_INT8, DFNT_INT16, DFNT_INT32, DFNT_UINT8, DFNT_UINT16, DFNT_UINT32.

For example:

type = HDF_IDL2HDFTYPE(SIZE(myData, /type))
SDdataset_id = HDF_SD_CREATE(f_id, "name", dims, HDF_TYPE=type)

INT

Set this keyword to indicate that the dataset is composed of 2-byte integers. Data will be stored with the HDF DFNT_INT16 data type. Setting this keyword is the same as setting either the SHORT keyword or the DFNT_INT16 keyword.

LONG

Set this keyword to indicate that the dataset is composed of longword integers. Data will be stored with the HDF DFNT_INT32 data type. Setting this keyword is the same as setting the DFNT_INT32 keyword.

SHORT

Set this keyword to indicate that the dataset is composed of 2-byte integers. Data will be stored with the HDF DFNT_INT16 data type. Setting this keyword is the same as setting either the INT keyword or the DFNT_INT16 keyword.

STRING

Set this keyword to indicate that the dataset is composed of strings. Data will be stored with the HDF DFNT_CHAR8 data type. Setting this keyword is the same as setting the DFNT_CHAR8 keyword.

Version History


4.0

Introduced

See Also


HDF_OPEN, HDF_SD_ENDACCESS, HDF_SD_SELECT



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