Routines (alphabetical) > Routines: H > HDF Routines > HDF_SD_REFTOINDEX

# HDF_SD_REFTOINDEX

The HDF_SD_REFTOINDEX function returns a scientific dataset’s index given its reference number and SD interface ID.

## Examples

; Initialize the SD interface:

SDinterface_id = HDF_SDSTART('demo.hdf')

; Define the reference number for which we want to search:

Reference_number = 66

; Return the index number:

index = HDF_SD_REFTOINDEX(SDinterface_id, Reference_number)

; Now the dataset can be accessed:

SDdataset_id = HDF_SD_SELECT(SDinterface_id, index)

; End access:

HDF_SD_ENDACCESS,SDdataset_id

HDF_SD_END, SDinterface_id

## Syntax

Result = HDF_SD_REFTOINDEX(SDinterface_id, Reference_number)

## Return Value

Returns the index number associated with the specified SD dataset.

## Arguments

### SDinterface_id

An SD interface ID as returned by HDF_SD_START.

### Reference_number

The SD reference number for the desired dataset.

## Keywords

None

## Version History

4.0 | Introduced

## See Also

HDF_SD_IDTOREF, HDF_SD_NAMETOINDEX