MATLAB Programming

7 Working with Scientific Data Formats
attr_idx = 0;
[attr, status] = hdfsd('readattr', sd_id, attr_idx);
attr =
my global attribute
Step 4: Selecting the Data Sets to Import. To select a data set, use
the SD API routine SDselect. InMATLAB,youusethe hdfsd function,
specifying as arguments:
• Name of the SD API routine, select in this case
• HDF4 SD file identifier (sd_id) returnedbySDstart
If SDselect finds the specified data set in the file, it returns an HDF4 SD
data set identifier, called sds_id intheexample. Ifitcannotfindthedata
set, it returns -1.
Note Do not confuse HDF4 SD file identifiers, named sd_id in the examples,
with HDF4 SD data set identifiers, named sds_id in the examples.
sds_id = hdfsd('select',sd_id,1)
Step 5: Getting Information About a Data Set. To read a data set, you
must get information about the data set, such as its name, size, and data
type. In the HDF4 SD API, you use the SDgetinfo routine to gather this
information. In MATLAB, use the hdfsd function, specifying as arguments:
• Name of the SD API routine, getinfo in this case
• HDF4 SD data set identifier (sds_id) returnedbySDselect
This code retrieves information about the data set identified by sds_id:
[dsname, dsndims, dsdims, dstype, dsatts, stat] =
hdfsd('getinfo',sds_id)
dsname =
A
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