How do I run a loop through multiple subjects?

Hello.

I'm sure this question has been asked a fair amount, and I've been attempting to look up the answer on various forums and tutorials, but they don't seem to answer my specific question.

If I have a group of subjects that I want to run a matlab command for, I understand how to set the subjects up as an array (subject_list = {'subject1','subject2'}), but if I am then attempting to run the command through these subjects, how would I enter the new 'subject_list' variable into the command? The command I have is:

roast('subject1/mri/T1.nii') where 'roast' is the command, and /mri/T1.nii is the same for each subject, so the only thing that would be changing is 'subject1' where I would like to loop all of my subjects.

Answer 1

[Robert U]

Hi Troy Tyszkowski,

loop through your subject list (replace the disp()-command by your 'roast'):

subject_list = {'subject1','subject2'};

for nSubject = 1:numel(subject_list)
    cmdString = strcat( subject_list{nSubject},'/mri/T1.nii');
    disp(cmdString)
end

Alternatively, use the cellfun()-function to shorten your code. Not so nice to read and debug, but quite quick in execution:

cellfun(@(cIn) disp(strcat(cIn,'/mri/T1.nii')),subject_list)

If you use paths you might want to look into fullfile() and filesep().

Kind regards,

Robert

[Troy Tyszkowski]

Hello Robert.

Thank you very much for your help! This is gonna cut down on my time by a large margin!

I'm not sure if it's already built into that code, but the 'roast' process doesn't work with every subject. Is there anything I would need to add to the code in order for it to not stop when there is an error and just move on to the next subject?

[Robert U]

Therefore, you can use try, catch-statement. Just leave the catch part empty or fill a warning in to keep track what subject did not work.