Can not read MAT file in another language

I have two MAT files. I can open A but can not open B in Julia.

When I used the command “@show(File)”. I got the below for File A:

F1 = MAT.MAT_HDF5.MatlabHDF5File(HDF5.File: (read-only) /Volumes/A.mat, true, false, 1108, false)

but the below for File B:

F2 = MAT.MAT_v5.Matlabv5File(IOStream(<file /Volumes/B.mat>), false, undef)

File A was created by someone I do not know, and File B was created by myself using the command below:

save(File_W, ‘Variable1’, ‘Variable2’);

I can open File B in Matlab easily. What is wrong with my file B? Is that because it is a special type of MAT file, i.e., HDF5? How do I create HDF5 flavored MAT files to make it more versatile? Thanks.

Answer 1

[John D'Errico]

My guess is Julia can read a .mat file created for an earlier release of MATLAB. Looking at the help for save, you can specify a different save format, able to be read into an earlier MATLAB release.

The default is "-v7" as you can see from the help. But you might try "-v6", or "-v4".

help save

 save - Save variables from workspace to file
    This MATLAB function saves all variables from the current workspace in a
    binary MATLAB file (MAT-file) named filename.

    Syntax
      save(filename)
      save(filename,variables)
      save(filename,variables,fmt)

      save(filename,variables,version)
      save(filename,variables,version,"-nocompression")
      save(filename,variables,"-append")
      save(filename,variables,"-append","-nocompression")

      save filename

    Input Arguments
      filename - Name of file
        "matlab.mat" (default) | string scalar | character vector
      variables - Names of variables to save
        string scalar | character vector
      fmt - File format
        "-mat" (default) | "-ascii" | "-ascii","-tabs" |
        "-ascii","-double" | "-ascii","-double","-tabs"
      version - MAT-file version
        "-v7" (default) | "-v7.3" | "-v6" | "-v4"

    Examples
      openExample('matlab/SaveAllWorkspaceVariablesToMATFileExample')
      openExample('matlab/SaveSpecificVariablestoMATFileExample')
      openExample('matlab/SaveDataToASCIIFileExample')
      openExample('matlab/SaveStructureFieldsasIndividualVariablesExample')
      openExample('matlab/SaveVariablesToVersion73MATFileExample')
      openExample('matlab/SaveVariablesToVersion7p3MATFileWithoutCompressionExample')
      openExample('matlab/AppendVariableToMATFileExample')
      openExample('matlab/AppendVariableToMATFileWithoutCompressionExample')
      openExample('matlab/SaveOnlyVariablesThatAlreadyExistInFileExample')

    See also clear, hgsave, load, matfile, regexp, saveas, whos

    Introduced in MATLAB before R2006a
    Documentation for save
       doc save

    Other uses of save

       cgproject/save
       COM.com/save
       COM/save
       imaq/save
       instrument/save
       matlab.diagram.ClassViewer/save
       mdevproject/save
       rmidata/save
       sim3d.Actor/save
       sim3d.World/save
       Simulink.Bus/save
       Simulink.CodeImporter/save
       Simulink.dialog.MaskPartReference/save
       Simulink.ModelWorkspace/save
       Simulink.ScenarioSimulation/save
       Simulink.sdi/save
       slcoverage.Filter/save
       slreq.LinkSet/save
       slreq.ReqSet/save

[Walter Roberson]

The opposite -- Julia can open the HDF5 based -v7.3 file but not the -v7 file.

So try

save(File_W, '-v7.3', ‘Variable1’, ‘Variable2’);

[John D'Errico]

I was pretty sure it was a choice of save version. It just went the other way.

[Leon]

'-v7.3' works.

Many thanks!