I have a *.h5 file with two groups - '/info' and '/data'. The '/info' group contains a series of 14 attributes that provide relevant information about the datasets in '/data'. I want to develop an 'attribute editor' for the '/info' attributes, but I am having difficultly modifying the existing attributes. I have tried two approaches using hdf5write and h5attput (from hdf5tools on matlab central).
Using hdf5write I can do the following:
attr = ‘new_info';
attr_details.Name = 'New_Attribute';
attr_details.AttachedTo = '/info’;
attr_details.AttachType = 'group';
hdf5write('myh5file.h5',attr_details, attr, 'WriteMode', 'append');
If the attribute didn’t exist previously, this seems to work fine – I get a new attribute ‘/info/New_Attribute’ whose Value.Data = ’new_info’. However, if I decide that I want to change this by continuing with
attr = ‘newer_info';
hdf5write('myh5file.h5',attr_details, attr, 'WriteMode', 'append');
I get the error
??? Error using ==> hdf5writec
writeH5Attr: Couldn't create attribute.
Error in ==> hdf5write at 143
hdf5writec(file, details, varargin{dset_idx});
Changing the ‘WriteMode’ to ‘overwrite’ doesn’t work either.
Using h5attput is similar, as I can create a new attribute with the command
h5attput('myh5file.h5','/info','New_Attribute','new_info’);
but trying to modify ‘New_Attribute’ gives an error, i.e.
h5attput('myh5file.h5','/info','New_Attribute','newer_info’);
??? Error using ==> hdf5lib2
The HDF5 library encountered an error: "Unknown error."
Error in ==> write at 36
H5ML.hdf5lib2('H5Awrite', varargin{:});
Error in ==> h5attput at 51
H5A.write(att_id,datatype_id,attvalue);
The difference with h5attput is that for numeric data, I am able to modify the attributes, so for example:
h5attput('myh5file.h5','/info','Numeric_Attribute',12);
creates the attribute ‘/info/Numeric_Attribute’ with Value = 12, which can be updated successfully with something like:
h5attput('myh5file.h5','/info','Numeric_Attribute',58);
So, in summary, I can use hdf5write or h5attput to create new attributes within an existing group, but I cannot modify the attributes using commands similar to those used to create them. The exception is using h5attput in the case where the attribute has a numeric value. I have also tried creating an h5 string object
new_info = hdf5.h5string('new_info’)
but neither hdf5write or h5attput accepts the h5 string as an input.
Thanks in advance for any input and ideas.
