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<HTML><HEAD>
<TITLE>HDF5 Tutorial - Creating Datasets in Groups
</TITLE>
</HEAD>
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[ <A HREF="title.html"><I>HDF5 Tutorial Top</I></A> ]
<H1>
<BIG><BIG><BIG><FONT COLOR="#c101cd">Creating Datasets in Groups</FONT>
</BIG></BIG></BIG></H1>
<hr noshade size=1>
<BODY>
<H2>Contents:</H2>
<UL>
<LI> <A HREF="#ds"> Creating datasets in groups</A>
<LI> Programming Example
<UL>
<LI> <A HREF="#desc">Description</A>
<!-- <LI> <A HREF="#rem">Remarks</A> -->
<LI> <A HREF="#fc">File Contents</A>
</UL>
</UL>
<HR>
<A NAME="ds">
<H2><U>Creating datasets in groups</U></H2>
We have shown how to create groups, datasets and attributes. In this section,
we show how to create datasets in groups. Recall that H5Dcreate creates a
dataset at the location specified by a location identifier and a name. Similar to
H5Gcreate, the location identifier can be a file identifier or a group identifier and the name can be
relative or absolute. The location identifier and the name together determine the
location where the dataset is to be created. If the location identifier and name
refers to a group, then the dataset is created in that group.
<H2> Programming Example</H2>
<A NAME="desc">
<H3><U>Description</U></H3>
This example shows how to create a dataset in a particular group.
It opens the file created in the previous example and creates two datasets.<BR>
[ <A HREF="examples/h5_crtgrpd.c">Download h5_crtgrpd.c</A> ]
<PRE>
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#include <hdf5.h>
#define FILE "groups.h5"
main() {
hid_t file_id, group_id, dataset_id, dataspace_id; /* identifiers */
hsize_t dims[2];
herr_t status;
int i, j, dset1_data[3][3], dset2_data[2][10];
/* Initialize the first dataset. */
for (i = 0; i < 3; i++)
for (j = 0; j < 3; j++)
dset1_data[i][j] = j + 1;
/* Initialize the second dataset. */
for (i = 0; i < 2; i++)
for (j = 0; j < 10; j++)
dset2_data[i][j] = j + 1;
/* Open an existing file. */
file_id = H5Fopen(FILE, H5F_ACC_RDWR, H5P_DEFAULT);
/* Create the data space for the first dataset. */
dims[0] = 3;
dims[1] = 3;
dataspace_id = H5Screate_simple(2, dims, NULL);
/* Create a dataset in group "MyGroup". */
dataset_id = H5Dcreate(file_id, "/MyGroup/dset1", H5T_STD_I32BE, dataspace_id
,
H5P_DEFAULT);
/* Write the first dataset. */
status = H5Dwrite(dataset_id, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT,
dset1_data);
/* Close the data space for the first dataset. */
status = H5Sclose(dataspace_id);
/* Close the first dataset. */
status = H5Dclose(dataset_id);
/* Open an existing group of the specified file. */
group_id = H5Gopen(file_id, "/MyGroup/Group_A");
/* Create the data space for the second dataset. */
dims[0] = 2;
dims[1] = 10;
dataspace_id = H5Screate_simple(2, dims, NULL);
/* Create the second dataset in group "Group_A". */
dataset_id = H5Dcreate(group_id, "dset2", H5T_STD_I32BE, dataspace_id, H5P_DEFAULT);
/* Write the second dataset. */
status = H5Dwrite(dataset_id, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT,
dset2_data);
/* Close the data space for the second dataset. */
status = H5Sclose(dataspace_id);
/* Close the second dataset */
status = H5Dclose(dataset_id);
/* Close the group. */
status = H5Gclose(group_id);
/* Close the file. */
status = H5Fclose(file_id);
}
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
</PRE>
<A NAME="fc">
<H3><U>File Contents</U></H3>
<P>
<B>Fig. 10.1</B> <I>The Contents of 'groups.h5'</I>
<PRE>
<IMG src="img005.gif"></PRE>
<!-- <IMG src="groups2.jpg" width="324" height="433"></PRE> -->
</PRE>
<B>Fig. 10.2</B> <I>'groups.h5' in DDL</I>
<PRE>
HDF5 "groups.h5" {
GROUP "/" {
GROUP "MyGroup" {
GROUP "Group_A" {
DATASET "dset2" {
DATATYPE { H5T_STD_I32BE }
DATASPACE { SIMPLE ( 2, 10 ) / ( 2, 10 ) }
DATA {
1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
1, 2, 3, 4, 5, 6, 7, 8, 9, 10
}
}
}
GROUP "Group_B" {
}
DATASET "dset1" {
DATATYPE { H5T_STD_I32BE }
DATASPACE { SIMPLE ( 3, 3 ) / ( 3, 3 ) }
DATA {
1, 2, 3,
1, 2, 3,
1, 2, 3
}
}
}
}
}
</PRE>
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<BR> <H6>Last Modified: August 27, 1999</H6><BR>
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