How do I load multiple .nii files in a function?

Hey everybody,

I'm struggling with loading multiple files inside a function with the 'path' as an input argument.

To make it more clear, here the part of the code that doesn't work:

    function [str, crb] = TAC_str_crb(nFrames, path, dynimg)

    fprintf(1, 'Reading from folder %s\n', path);
    DynImg = zeros(nFrames, 340, 330, 760);

    for f=1:nFrames 
        sprintf(dynimg, f);
        filename = fullfile(path, dynimg);  
        fprintf(1, 'Loading %s...\n', dynimg);

        fid = fopen(filename);   
        if(fid==-1) fprintf(2,'File not found\n');end
        fseek(fid, 352, 'bof');
        I = reshape(fread(fid, Inf, 'float'), 340, 330, 760);
        fclose(fid);

        DynImg(f,:,:,:) = I;    
    end

I tried to use the function like this:

    TAC_str_crb(20, '/resalk/home/dyn', 'mouse1_frame%d.nii')

The problem is, that Matlab always thinks that the filename includes %d and doesn't count through all my files and therefore the fseek command doesn't work. The error message I get is:

    Reading from folder /resalk/home/dyn
    Loading mouse1_frame%d.nii...
    File not found
    Error using fseek
    Invalid file identifier.  Use fopen to generate a valid file identifier.

Would be great if someone could help me solve that problem.

Thanks in advance!

[Weird Rando]

Probably '\' not '/'

[Walter Roberson]

No, / works for MS Windows as well as Mac and Linux, and you need to be careful if you use \ in sprintf

Answer 1

[Walter Roberson]

You do the sprintf and discard the result. Then you use the version with the percent in it.

Answer 2

[Kerst Resalk]

Thanks for your answer Walter!

To be honest, I am not entirely sure what you mean. How do I discard the result of the sprintf? I'm pretty new to all that Matlab stuff, so my apologies if that question sounds kind of stupid.

[Walter Roberson]

Your line

sprintf(dynimg, f);

That calls sprintf() passing in dynimg as the first argument and f as the second argument. That creates a string result based upon the format and values. That returns the string to "ans". Then, the semi-colon tells MATLAB to throw away "ans" instead of automatically displaying it.

Change

       sprintf(dynimg, f);
        filename = fullfile(path, dynimg);

to

       thisfile = sprintf(dynimg, f);
        filename = fullfile(path, thisfile);

This stores the result of the sprintf() and passes it on to fullfile.

[Kerst Resalk]

I get it, thanks a lot for that explanation!