How to iterate a structure name and save directory in a for loop?

I am trying to use a for loop that saves parameters for 10 different files into a structure, but I am not sure how to get the name of each structure to iterate. My final result should be 10 different structures saved into a directory with the name for the structures being rate100,rate150,rate200,..... So far my for loop has two issues. The first is I am unable to use ['rate' num2str(cnt)] for the structure name, and the second is I am unsure how to get the save path to be my pathname + 'rate' + #. How can I change my for loop to get the structure name to iterate and why does my format for the save command not work?

saveDir = 'my/path/name
cnt = 50;
for j=1:10
    cnt = cnt+50;
    ['rate' num2str(cnt)].minTime = tmin;
    ['rate' num2str(cnt)].maxTime = tmax;
    % Save structure
    save([saveDir '/rate' num2str(cnt) '.mat'],['rate' num2str(cnt)]);
end

[Stephen23]

"...with the name for the structures being rate100,rate150,rate200,..... So far my for loop has two issues."

The main issue is that you are forcing meta-data into variable names.

Forcing meta-data into variable names is usually a sign that you are doing something wrong:

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

If you simply stored that meta-data inside the structure and used exactly the same variable names in every MAT file, then your code would be simpler, more efficient, and much more robust:

saveDir = 'my/path/name';
for k = ..
    S.minTime = tmin;
    S.maxTime = tmax;
    S.rate = whatever_meta_data_you_want;
    % Save structure
    F = [saveDir,'/rate',num2str(cnt),'.mat'];
    save(F, 'S'); % simpler and much more robust
end

In contrast, your approach of forcing meta-data into the variable names suffers from a number of problems:

https://www.mathworks.com/matlabcentral/answers/225435-save-variable-as-string-from-user-input#answer_184104

(that explanation is for fieldnames, but it applies just as much to forcing meta-data into variable names)

Answer 1

[Walter Roberson]

saveDir = 'my/path/name
for j=1:10
    cnt = 50 * (j+1);
    clear savestruct
    ratefield = "rate" + cnt;
    savestruct.(ratefield).minTime = tmin;
    savestruct.(ratefield).maxTime = tmax;
    filename = fullfile(saveDir, ratefield + ".mat");
    save(filename, '-struct', 'savestruct');
end

Notice this contains no dynamic variable names -- but it does contain dynamic field names within a structure.

When you save a structure with the -struct option, then instead of saving the struct as a variable, it saves each field of the struct as a variable.

Answer 2

[Voss]

saveDir = 'my/path/name';
cnt = 50;
for j=1:10
    cnt = cnt+50;
    S = struct('minTime',tmin,'maxTime',tmax);
    % Save structure
    filename = fullfile(saveDir,sprintf('rate%d.mat',cnt));
    save(filename,'-struct','S');
end

[Walter Roberson]

This would save individual variables minTime and maxTime in the file, but the requirement is "My final result should be 10 different structures saved into a directory with the name for the structures being rate100,rate150,rate200"

[Voss]

Yes. I interpret that to mean 10 different mat files, each containing a minTime and a maxTime.

[Walter Roberson]

"The first is I am unable to use ['rate' num2str(cnt)] for the structure name, and the second is I am unsure how to get the save path to be my pathname + 'rate' + #"

So the user is distinguishing between structure name and file name, and asked that what is stored in the file is a structure

[Voss]

Yes, but the file name is the same as the structure name, and it'll be a struct when she load()s it.

[Stephen23]

Alternative avoiding the intermediate structure:

for k = ..
    ..
    save(filename,'tmin','tmax');
end