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

HDF_SD_SETINFO

HDF_SD_SETINFO

The HDF_SD_SETINFO procedure sets information about an SD dataset.

Setting a label, unit, format, or coordinate system string that has more than 256 characters can have unpredictable results.

Examples


; Open an HDF file:
SDinterface_id = HDF_SD_START('demo.hdf', /RDWR)
; Define a new dataset for the file:
SDdataset_id = HDF_SD_CREATE(SDinterface_id, 'variable1', [10, 20], /DOUBLE)
; Create a calibration data structure:
CAL={Cal:1.0D, Cal_Err:0.1D, Offset:2.5D, Offset_Err:0.1D, $
   Num_Type:6L}
; Set information about the dataset:
HDF_SD_SETINFO, SDdataset_id, LABEL='label1', unit='unit1', $
   format='format1', coordsys='coord1', FILL=999.991, $
   RANGE=[99.99,-78], caldata=CAL
; Retrieve the information:
HDF_SD_GETINFO, SDdataset_id, LABEL=l, UNIT=u, FORMAT=f, $
   COORDSYS=c, FILL=fill, RANGE=r, CALDATA=cd, $
   NDIMS=ndims, DIMS=dims, TYPE=ty
; Print information about the returned variables:
HELP, l, u, f, c, fill, r, cd, ndims, dims, ty
; Print the range:
PRINT, r
; Print the calibration data:
PRINT, cd
; Print the dimensions:
PRINT, dims
; Close the SD interface:
HDF_SD_ENDACCESS, SDdataset_id
HDF_SD_END, SDinterface_id

IDL Output

L STRING = 'label1'
U STRING = 'unit1'
F STRING = 'format1'
C STRING = 'coord1'
FILL DOUBLE = 999.99103
R DOUBLE = Array(2)
CD STRUCT = -> < Anonymous > Array(1)
NDIMS LONG = 2
DIMS LONG = Array(2)
TY STRING = 'DOUBLE'
 
-78.000000 99.989998 
 
{ 1.0000000 0.10000000 2.5000000 0.10000000 6} 
 
10 20

Syntax


HDF_SD_SETINFO, SDdataset_id [, CALDATA=structure] [, COORDSYS=string] [, FILL=value] [, FORMAT=string] [, LABEL=string] [, RANGE=[max, min]] [, UNIT=string]

Arguments


SDdataset_id

An SD dataset ID as returned by HDF_SD _SELECT or HDF_SD_CREATE.

Keywords


CALDATA

Set this keyword to a structure that contains the calibration data. This structure must contain five tags as shown below. The first four tags are of double-precision floating-point type. The fifth tag should be a long integer that specifies the HDF number type. The structure should have the following form:

CALDATA={ Cal: 0.0D $         ;Calibration Factor
      Cal_Err: 0.0D $         ;Calibration Error
       Offset: 0.0D $         ;Uncalibrated Offset
       Offset_Err: 0.0D $     ;Uncalibrated Offset Error
       Num_Type: 0L }          ;Number Type of Uncalibrated Data

The relationship between HDF and IDL number types is illustrated by the following table:

HDF Number Type

IDL Data Type

0L

UNDEFINED

3L

STRING

21L

BYTE

22L

INTEGER

24L

LONG INTEGER

5L

FLOATING-POINT

6L

DOUBLE-PRECISION

The relationship between the calibrated data (CD) and the uncalibrated data (UD) is given by the equation:

CD = Cal * (UD - Offset)

Cal and Offset are the values of the Cal and Offset structure fields described above.

COORDSYS

Set this keyword to a string to be used as the SD dataset coordinate system.

FILL

Set this keyword to the fill value of the SD dataset.

FORMAT

Set this keyword to a string to be used as the SD dataset format.

LABEL

Set this keyword to a string to be used as the SD dataset label.

RANGE

Set this keyword to a two dimensional array that contains the minimum and maximum values of the SD dataset.

UNIT

Set this keyword to a string to be used as the SD dataset units.

Version History


4.0

Introduced

See Also


HDF_SD_END, HDF_SD_ENDACCESS, HDF_SD_GETINFO, HDF_SD_START



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