MATLAB Programming

7 Working with Scientific Data Formats
model of one particular HDF4 API: the HDF4 Scientific Data (SD) API. For a
complete list of the HDF4 APIs supported by MATLAB and the functions you
use to access each one, see the hdf reference page.
Note This section does not attempt to describe all HDF4 features and
routines. To use the MATLAB HDF4 functions effectively, you must refer to
the official NCSA documentation at the HDF Web site (www.hdfgroup.org).
Topics covered include
• “Understanding the HDF4 to MATLAB Syntax Mapping” on page 7-56
• “Example: Importing Data Using the HDF4 SD API Functions” on page
7-57
• “Example: Exporting Data Using the HDF4 SD API Functions” on page
7-63
• “Using the MATLAB HDF4 Utility API” on page 7-70
Understanding the HDF4 to MATLAB Syntax Mapping
Each HDF4 API includes many individual routines that you use to read
data from files, write data to files, and perform other related functions. For
example,theHDF4ScientificData(SD) API includes separate C routines to
open (SDopen), close (SDend), andreaddata(SDreaddata).
Instead of supporting each routine in the HDF4 APIs, MATLAB provides a
single function that serves as a gateway to all the routines in a particular
HDF4 API. For example, the HDF Scientific Data (SD) API includes the C
routine SDend to close an HDF4 file:
status = SDend(sd_id); /* C code */
To call this routine from MATLAB, use the MATLAB function associated with
the SD API, hdfsd. Youmustspecifythenameoftheroutine,minustheAPI
acronym, as the first argument and pass any other required arguments to the
routine in the order they are expected. For example,
status = hdfsd('end',sd_id); % MATLAB code
7-56