??? Error using ==> fprintf Invalid file identifier. Use fopen to generate a valid file identifier.

Hi, I get this error when running a statistical analysis. Can anyone help me with that? I always used this script and always worked. I have just moved to a group license and everything stopped working. I am using Matlab 2010a (MAC OSX 64-bit). Many thanks. Here is the code:

for cd = 1:NSTIM,
    fid = fopen([pwd '/' directory '/Stats_' vec_info(cd).evmarker],'w');
    fprintf(fid,'%s\n',['                   HbO_2                                      HHb         ']);
    fprintf(fid,'%s',['Channel    P-val   H-val   PosMchge  Mchange Ntrials']);
    fprintf(fid,'%s\n',['    P-val   H-val   PosMchge  Mchange Ntrials']);
    for ch = 1:NTRACES,
        fprintf(fid,'%6f    %6.8f   %6f %6.8f %6.8f   %6f ',ch, Pval_STIM_oxy(cd,ch),Hval_STIM_oxy(cd,ch),pos_oxy(ch),mean_oxy(ch,cd),Ntrials_oxy(ch,cd));
        fprintf(fid,'%6.8f   %6f %6.8f  %6.8f   %6f\n',Pval_STIM_deoxy(cd,ch),Hval_STIM_deoxy(cd,ch),pos_deoxy(ch),mean_deoxy(ch,cd),Ntrials_deoxy(ch,cd));
    end
    fclose(fid);

Answer 1

[per isakson]

1. legal file name? what string is produced by "[pwd '/' directory '/Stats_' vec_info(cd).evmarker]"?
2. add assert( fid >= 3, ... ) to the code
3. use [ fid, message] = fopen( filename, ...) and output message with the the message of assert

[Maria]

Thanks for your quick answer. Where exactly should I change the code? Where can I use the [fid, message] command? Thanks

[Walter Roberson]

You currently have

fid = fopen( [etc]

change that to

[fid, message] = fopen( [etc]

Answer 2

[Jan]

Obviously this line fails:

fid = fopen([pwd '/' directory '/Stats_' vec_info(cd).evmarker],'w');

You could and should catch corresponding problems using:

[fid, msg] = fopen(fullfile(pwd, directory, ['Stats_', vec_info(cd).evmarker], 'w');
if fid == -1
  error(msg);
end

I guess, that either the file is existing already and write-protected, or you do not have write permissions to the folder.

FULLFILE considers trailing file separators, e.g. if the current directory is "C:\".

[muqeet ahmad [phone]]

 [fid, msg] = fopen(fullfile(pwd, directory, ['Stats_', vec_info(cd).evmarker], 'w'); if fid == -1 error(msg); end

what if i want to change the directory of file, is it possible?

[Walter Roberson]

Remove the pwd and set the variable named directory to whatever directory name you want to write to