MATLAB Programming

Hierarchical Data Format (HDF5) Files
1 Create the MATLAB variable that you want to write to the HDF5 file. The
examples creates a three-dimensional array of uint8 data.
testdata = uint8(ones(5,10,3));
2 CreatetheHDF5fileoropenanexistingfile.Theexamplecreatesanew
HDF5 file, named my_file.h5, in the system temp directory.
filename = fullfile(tempdir,'my_file.h5');
fileID = H5F.create(filename,'H5F_ACC_TRUNC','H5P_DEFAULT','H5P_DEFAULT');
In HDF5, you use the H5Fcreate function to create a file. The example
uses the MATLAB equivalent, H5F.create. As arguments, specify the
name you want to assign to the file, the type of access you want to the file
('H5F_ACC_TRUNC' in the example), and optional additional characteristics
specified by a file creation property list and a file access property list. This
example uses default values for these property lists ('H5P_DEFAULT').
Intheexample,notehowtheCconstantsarepassedtotheMATLAB
functions as strings. The function returns an ID to the HDF5 file.
3 Create the data set in the file to hold the MATLAB variable. In the HDF5
programming model, you must define the data type and dimensionality
(dataspace)ofthedatasetasseparateentities.
a Specify the data type used by the data set. In HDF5, you use the
H5Tcopy function to create integer or floating-point data types. The
example uses the corresponding MATLAB function, H5T.copy, to create
a uint8 data type because the MATLAB data is uint8. The function
returns a data type ID.
datatypeID = H5T.copy('H5T_NATIVE_UINT8');
b Specify the dimensions of the data set. In HDF5, you use the
H5Screate_simple routinetocreateadataspace.Theexampleusesthe
corresponding MATLAB function, H5S.create_simple, tospecifythe
dimensions. The function returns a data space ID.
dims(1) = 5;
dims(2) = 10;
dims(3) = 3
dataspaceID = H5S.create_simple(3, dims, []);
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