matlab fprintf error? please help

Hi all,

I am very very new to matlab, and I am trying to run a script that will read my txt files and write it on my xlsx file. I have about 120 txt files, so I am trying to run a script on them, but I keep having this fprintf error on a part of my script.

fid = fopen(sprintf('%s/Timeseries.ROIs/%s_timeseries.xlsx',rootdir,rois{roi}),'w'); 
colhdrs = {'Subject','Group','Gender','Subject','Condition','-4.4', '-2.2', '0', '2.2', '4.4', '6.6', '8.8', '11', '12.2'}; 
fprintf(fid,'%s\t',colhdrs{:}); fprintf(fid,'\n');

I keep facing an error with the script line below.

frpintf(fid, '%s \ t', colhdrs {:}); 
saying that it has Invalid file identifier. Use fopen to generate a valid file identifier. 

Again, I am very new so any help would be much appreciated. Thank you so much!

Answer 1

[per isakson]

Most likely, fid = fopen(...), failed and return a negative value to fid.

Replace

fid = fopen(sprintf('%s/Timeseries.ROIs/%s_timeseries.xlsx',rootdir,rois{roi}),'w'); 

by

ffs = fullfile( rootdir, 'Timeseries.ROIs', [rois{roi},'_timeseries.xlsx'] );
[fid,msg] = fopen( ffs, 'w' );

and run the script and inspect the values of ffs, fid and msg.

See: Debug a MATLAB Program

[Walter Roberson]

And remember that when you fopen() a file for 'w', that the underlying operating system will not automatically create any missing directories. If rootdir is not a directiory, or if Timeseries.ROIs is not a directory within rootdir, then the fopen() would fail.