MATLAB Programming

7 Working with Scientific Data Formats
Determining the Contents of an HDF5 File
HDF5 files can contain data and metadata, called attributes. HDF5files
organize the data and metadata in a hierarchical structure similar to the
hierarchical structure of a UNIX file system.
In an HDF5 file, the directories in the hierarchy are called groups. Agroup
can contain other groups, data sets, attributes, links, and data types. A data
set is a collection of data, such as a multidimensional numeric array or string.
An attribute is any data that is associated with another entity, such as a data
set. A link is similar to a UNIX file system symbolic link. Links are a way to
reference data without having to make a copy of the data.
Data types are a description of the data in the data set or attribute. Data
types tell how to interpret the data in the data set. For example, a file might
contain a data type called “Reading” that is comprised of three elements: a
longitude value, a latitude value, and a temperature value.
To explore the hierarchical organization of an HDF5 file, use the hdf5info
function. For example, to find out what the sample HDF5 file, example.h5,
contains, use this syntax:
fileinfo = hdf5info('example.h5');
hdf5info returns a structure that contains various information about the
HDF5 file, including the name of the file and the version of the HDF5 library
that MATLAB is using:
fileinfo =
Filename: 'example.h5'
LibVersion: '1.6.5'
Offset: 0
FileSize: 8172
GroupHierarchy: [1x1 struct]
In the information returned by hdf5info, look at the GroupHierarchy field.
This field is a structure that describes the top-level group in the file, called
the root group. Using the UNIX convention, HDF5 names this top-level group
/ (forward slash), as shown in the Name field of the GroupHierarchy structure.
toplevel = fileinfo.GroupHierarchy
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