I am facing an error "invalid file identifier" while using fprintf and fopen

in my script i am trying to store my result variable using the following line of code,

if(ledaOrLocal ==0)
    sdir        = 'F:/MS Thesis/Data/Dataset/'; 
    resultDir   = 'F:/MS Thesis/Data/Results/'; 
    outputFileName = [resultDir, 'ResultsForParameterTrainingV1To_', num2str(kernel_param.idataset), '.txt']; 
    file_1 = fopen(outputFileName,'w');
    for version = myStart:totalVersions
        disp('-------------------------------------------------');
        fprintf(file_1,'\n'); 
        fclose(file_1);

but facing the issue of "invalide identifier, the error snap is attached, how it could be solved, help is highly appreciated. thanks

Answer 1

[Jan]

Whenever you try to open a file, check the success:

[file_1, msg] = fopen(outputFileName, 'w');
assert(file_1 > 0, msg);

Now you see an error message, if the file cannot be opened.

Maybe the directory is not existing or you do not have write permissions in this folder.

Use fullfile instead of concatenating the char arrays:

outputFileName = [resultDir, 'ResultsForParameterTrainingV1To_', num2str(kernel_param.idataset), '.txt'];
% Or safer:
outputFileName = fullfile(resultDir, sprintf('ResultsForParameterTrainingV1To_%d.txt', kernel_param.idataset));