Trying to pass a variable name for a file in a for loop to xlsread

I'm trying to use xlsread to open a variable filename on each iteration of a for loop. The code I initially used was

for vj=1:prime_file_num
    BaseName='15_File_';
    k=prime_file_num1(vj,1);
    FileName=[BaseName,num2str(k)];
    [~,~,rawS] = xlsread(FileName);

which worked for one iteration, then just seemed to grind away forever trying to read the next File, and now just grinds even on the first iteration. I tried changing the code to

    for vj=1:prime_file_num
        BaseName='15_File_';
        k=prime_file_num1(vj,1);
        FileName=[BaseName,num2str(k)];
        pathname = 'C:\Documents\MATLAB\FileName.xlsx';
        [~,~,rawS] = xlsread(pathname);

But that just returns the error that xlsread can't find the file--its trying to open a file named 'C:\Documents\MATLAB\FileName.xlsx, rather than '15_File_2' for example.

Can anybody tell me what I'm doing wrong or is what I'm trying even possible. Thanks

[Stephen23]

The standard MATLAB approach is to use FULLFILE to join the filepath and filename:

BaseName = '15_File_%d'; % no need to redefine this in the loop
pathname = 'C:\Documents\MATLAB'; % ditto
for vj = 1:prime_file_num
    fnm = sprintf(BaseName,prime_file_num1(vj,1)):
    [~,~,rawS] = xlsread(fullfile(pathname,fnm));
    ..
end

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

[Mark Bodner]

The files attempting to open don't follow integers though but the content of the prime_file_num1(vj,1). That is on successive iterations the files are 15_File_2, 15_File_3, 15_File_5, 15_File_7... and not 15_File_1, 15_File_2, 15_File_3... so does this still work?

[Mark Bodner]

Also tried the code and its still just trying to open a file calle 'C:\Documents\MATLAB\FileName.xlsx'. Its not treating it as a path but rather as the file name itself. So there's obviously something missing?

[Stephen23]

"so does this still work?"

Yes. Look at the code: it uses prime_file_num1 to define the values used in the filenames.

"So there's obviously something missing?"

Make sure that pathname does not include "Filename.xlsx" : check my previous comment again!

Answer 1

[Jan]

pathname = 'C:\Documents\MATLAB\FileName.xlsx';

This is a fixed CHAR vector and does not consider the variable FileName.

Stephen's appraoch is working, if the path name is fixed:

BaseName = '15_File_%d.xlsx';  % [EDITED, file extension added]
pathname = 'C:\Documents\MATLAB\';
for vj = 1:prime_file_num
    filename   = sprintf(BaseName, prime_file_num1(vj, 1));
    file       = fullfile(pathname, filename);
    % [~,~,rawS] = xlsread(file);
    disp(file);   % For testing
    ...
end

[Mark Bodner]

For whatever reason, that doesn't work! It just keeps trying to open a file called 'C:\Documents\MATLAB\15_File_2'. It doesn't see anything as a pathway, but rather as the name of the file trying to be read, and then returns the error that the file is not found. I don't know what is going wrong.

[Jan]

No, my code does not open anything. It displays the file names only. This means, that you are doing something else and I cannot know, what it is.

Solve the problem step by step. Start with the shown code. Does it work? Do you see the different file names? If all filenames are equal, you have shown, that prime_file_num1 contains only the value 2.

Please post the output of the above code, if you get any problems there.

If this is working proceed with the next step to uncomment the xlsread() command. Do you get an error message now? If so, please post a copy of the complete message.