How to create a HDF5 group with only attributes

Writing an attribute to a group that already has a dataset works fine:

h5create("sample.hdf5", "/group/dataset", 1:3)
h5writeatt("sample.hdf5", "/group/", "attribute", 3.14)

But I cannot create attributes in files that do not alredy exist:

h5create("sample2.hdf5", "/group1/dataset", 1:3)
h5writeatt("sample2.hdf5", "/group2/", "attribute", 3.14)

Error using hdf5lib2

The HDF5 library encountered an error and produced the following stack trace information:

H5G_loc_find_cb object 'group2' doesn't exist

(...)

There is no "create attribute" function as there is for datasets. I understand this constraint may be there for a purpose, but is there a workaround?

Answer 1

[Manish]

Hi Hamo,I encountered a similar issue and found a workaround.

Before writing the attribute, explicitly create the group by opening the file.

Here is the code implementation:

h5create("sample.hdf5", "/group/dataset", [1 3]);
h5writeatt("sample.hdf5", "/group/", "attribute", 3.14);
h5create("sample2.hdf5", "/group1/dataset", [1 3]);

% Workaround: 
fileID = H5F.open('sample2.hdf5', 'H5F_ACC_RDWR', 'H5P_DEFAULT');
groupID = H5G.create(fileID, '/group2', 'H5P_DEFAULT', 'H5P_DEFAULT', 'H5P_DEFAULT');
H5G.close(groupID);
H5F.close(fileID);

% Now write the attribute to the newly created group
h5writeatt("sample2.hdf5", "/group2/", "attribute",3.14);

It solved for me, Hope this solves for you!