How to use a for cycle for opening .mat files

Hi,

In the directory c:\MAT (it's not my workspace directory), I have the following .mat files:

A1B1.mat

A1B2.mat

A1B3.mat

A2B1.mat

A2B2.mat

A2B3.mat

A3B1.mat

A3B2.mat

A3B3.mat

How can I automate the opening/import of them, for example, using a for cycle, saving each .mat file in a new variable?

Best regards,

Answer 1

[Stephen23]

The general concept is shown here:

https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

You can easily store the imported data in the same structure as DIR returns, e.g.:

P = 'C:\MAT';
S = dir(fullfile(P,'*.mat'));
for k = 1:numel(S)
    F = fullfile(P,S(k).name);
    S(k).data = load(F);
end

All of the imported file data will be stored in the structure S. For example, for the second file:

S(2).name % filename
S(2).data % structure of the imported data

If each file contains exactly one variable of the same name then you can simplify the later processing by specifying that variable when importing:

P = 'C:\MAT';
S = dir(fullfile(P,'*.mat'));
for k = 1:numel(S)
    F = fullfile(P,S(k).name);
    T = load(F);
    S(k).data = T.nameOfTheVariable;
end

Note that after then loop you can use this syntax, which might make processing your data easier:

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

[Hugo]

Thank you for your useful answer. your solution works.

Now, if I would like to load each .mat file that your code originates into a variable,, how shall my "load" command be?

[Stephen23]

"Now, if I would like to load each .mat file that your code originates into a variable"

They are already in a variable, the structure S. You can access them simply and efficiently using indexing.

If you want each file loaded into a separate, dynamically named variable, you might like to read this:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Answer 2

[Image Analyst]

See the FAQ:

https://matlab.fandom.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F