fread() help. "Error using fread: Invalid file identifier..."

Hello everyone,

I am currently working in analyzing a set of data in the PTU format using a script called "Read_PTU_V1.m". However, I had an issue while running it. After the program opened a dialog box to select a file from my PC, I ran into the following error.

Error using fread
Invalid file identifier. Use fopen to generate a valid file identifier.

Error in Read_PTU_V1 (line 57)
    Magic = fread(fid, 8, '*char');

I have attached the section that I believe will present a good idea on what is the problem I have. It starts in line 53 and goes down to line 60.

      % start Main program
     [filename, pathname]=uigetfile('*.ptu', 'T-Mode data:'); %Opens dialog box to manually select the file using file explorer
    fid=fopen(filepath);
    
    Magic = fread(fid, 8, '*char');
    if not(strcmp(Magic(Magic~=0)','PQTTTR'))
        error('Magic invalid, this is not an PTU file.');
    end; 

I didn't write this script and honestly have no idea how to make it work. Please help a poor man with no matlab experience. I have attached the file as an extra resource.

Answer 1

[dpb]

    [filename, pathname]=uigetfile('*.ptu', 'T-Mode data:'); %Opens dialog box to manually select the file using file explorer
    fid=fopen(filepath);

Well, no, this could never have worked as written...the script returns the file and path in variables filename and pathname but then uses something entirely different to try open a file. That makes no sense whatsoever.

You'll have much better chance with something like

[filename, pathname]=uigetfile('*.ptu', 'T-Mode data:'); %Opens dialog box to manually select the file using file explorer
fid=fopen(fullfile(pathname,filename),'r');

You should then by all rights check for fid<0 and show any error messages if so...there's examples in the doc for fopen for such.

Doesn't engender much confidence in the rest of the script with such a horrible problem right off the bat...presuming it's as was distributed and not somehow butchered by other than the author.

[Jose Godinez]

Thank you so much. I wish I have never been given the task to make this work!