Converting a .mat file with multiple variables from v5 to v7

I have a .mat file that contains variables of 120 trials of behavioural data. The file was saved in v5 format, which doesn't seem to be supported so I am trying to save it as v7 using

save('rsvp_data.mat', '*', '-v7')

using the '*' as wildcard to select all the variables instead of writing all 120 of them out.

I get the error:

Error using save

Unable to write file rsvp_data.mat: No such file or directory.

I am in the correct directory and path and all the relevant files are in the directory/path. The original file is named rsvp_data.mat. Should it be renamed to something else? I have tried saving the workspace also, but it doesn't have the 'save as' option, only 'save'.

Does anyone have any advice for me?

[Walter Roberson]

save('rsvp_data.mat', '-v7')

could be used to store all the variables in the current workspace.

[Antoinette Burger]

Thank you@Walter Roberson I still get the same error that the file/directory doesn't exit. It's very strange.

[Walter Roberson]

I would only expect that message to appear on a save under two different circumstances:

1. the current directory in MATLAB is one that no longer exists. This would have required that the directory was deleted after the user changed to that directory.
2. the current directory in MATLAB is set to a network drive such as Microsoft OneDrive, and the network drive is acting up. I have seen more reports of that for OneDrive in particular than for other drives such as Google Drive, but hypothetically OneDrive might perhaps just be used a lot more than the others... so I do not know if it is worse than the others or if it is just used so much more than a lower portion would still give more reports than the hypothetically worse drives.

[Antoinette Burger]

Thank you @Walter Roberson, I appreciate your help!

Answer 1

[Walter Roberson]

The file was saved in v5 format, which doesn't seem to be supported

Supported by what? And what are you looking at to see that it was saved in v5 rather than some later version?

test = randi([-9 9], 3, 3)

test = 3×3

4 -9 -2 -4 9 -3 -2 -2 7

save('test6.mat', '-v6')
save('test7.mat', '-v7')
save('test73.mat', '-v7.3')

fid = fopen('test6.mat', 'r'); b6 = fread(fid, [1 64], '*uint8'); fclose(fid);
fid = fopen('test7.mat', 'r'); b7 = fread(fid, [1 64], '*uint8'); fclose(fid);
fid = fopen('test73.mat', 'r'); b73 = fread(fid, [1 64], '*uint8'); fclose(fid);

fprintf('\nv6\n');

v6

disp(b6)

  Columns 1 through 33

    77    65    84    76    65    66    32    53    46    48    32    77    65    84    45   102   105   108   101    44    32    80   108    97   116   102   111   114   109    58    32    71    76

  Columns 34 through 64

    78    88    65    54    52    44    32    67   114   101    97   116   101   100    32   111   110    58    32    87   101   100    32    77    97   114    32    32    49    32    50

disp(char(b6));

MATLAB 5.0 MAT-file, Platform: GLNXA64, Created on: Wed Mar  1 2

fprintf('\nv7\n');

v7

disp(b7)

  Columns 1 through 33

    77    65    84    76    65    66    32    53    46    48    32    77    65    84    45   102   105   108   101    44    32    80   108    97   116   102   111   114   109    58    32    71    76

  Columns 34 through 64

    78    88    65    54    52    44    32    67   114   101    97   116   101   100    32   111   110    58    32    87   101   100    32    77    97   114    32    32    49    32    50

disp(char(b7));

MATLAB 5.0 MAT-file, Platform: GLNXA64, Created on: Wed Mar  1 2

fprintf('\nv73\n');

v73

disp(b73)

  Columns 1 through 33

    77    65    84    76    65    66    32    55    46    51    32    77    65    84    45   102   105   108   101    44    32    80   108    97   116   102   111   114   109    58    32    71    76

  Columns 34 through 64

    78    88    65    54    52    44    32    67   114   101    97   116   101   100    32   111   110    58    32    87   101   100    32    77    97   114    32    32    49    32    50

disp(char(b73));

MATLAB 7.3 MAT-file, Platform: GLNXA64, Created on: Wed Mar  1 2

As you can see, v6 and v7 files both have 'MATLAB 5.0 MAT-file' in the header. v5 v6 v7 files all use the same fundamental format -- just additional capabilities were activated in the later releases.

v7.3 files are a fundamentally different format (based on HD5F) and have a different header.

[Antoinette Burger]

Sorry @Walter Roberson, I meant supported by scipy.io loadmat. The documentation for scipy.io loadmat refers to v4, v6, v7 and v7.3, and there has been another question regarding this, with the recommendation being to resave the file in a different version.

[Walter Roberson]

Okay, but what software produced the files believed to be v5 files ?

[Antoinette Burger]

This is the feedback in terminal when checking the file:

antbu@MacBook-Air notebooks % file /Volumes/2020_MRS_CI/RSVP_data/Epilepsy/Monitoring/2021-01-18_e0011XQ_01/rsvp_data.mat

/Volumes/2020_MRS_CI/RSVP_data/Epilepsy/Monitoring/2021-01-18_e0011XQ_01/rsvp_data.mat: Matlab v5 mat-file (little endian) version 0x100, platform MACI64, created Wed Mar 1 15:59:18 2023

The file was created by Monkeylogic, an app that runs in Matlab.

[Walter Roberson]

test = randi([-9 9], 3, 3)

test = 3×3

0 -9 -1 6 9 0 8 9 -8

save('test6.mat', '-v6')
save('test7.mat', '-v7')
save('test73.mat', '-v7.3')

!file test6.mat

test6.mat: Matlab v5 mat-file (little endian) version 0x0100

!file test7.mat

test7.mat: Matlab v5 mat-file (little endian) version 0x0100

!file test73.mat

test73.mat: Hierarchical Data Format (version 5) with 512 bytes user block

As I said, -v5 through -v7 all say MATLAB 5.0 file in the header, and file reports v5 for all of them, but that does not prove they were created with v5 specifically.

[Antoinette Burger]

I understand, thank you @Walter Roberson

[Walter Roberson]

https://monkeylogic.nimh.nih.gov/docs_GettingStarted.html#FormatsSupported

MAT is MATLAB’s native data format. NIMH ML uses the default MAT-file format that is set in the MATLAB Preferences.

That is, monkeylogic is just using save() without specifying a -v option to save() . And since '-v5' is not a supported option, it could not have been saved in the original unmodified MAT 5.0 format.

[Antoinette Burger]

Thank you @walter robertson, we went with what we saw in the file description in terminal. Your explanation helps a lot to understand the file formats.