Error using Fseek. Invalid filer identifier, use fopen to generate a valid file identifier.

I get an error stating "Invalid file identifier. Use fopen to generate a valid file identifier."

Folders are 45meas.fid, 55meas.fid, 65meas.fid, etc. (temps+meas)

center_ppm = 5.8;
region_bounds_ppm = [2.924, 2.237];
temps = [45, 55, 65, 75, 85, 95, 100, 105, 110, 115]; %If you have any different temperatures for any reason adjust here

%% Read in and process NMR Data

for ii = 1:length (temps)
    file_temp = fopen(strcat(num2str(temps(ii)),'C.fid/fid'));
    fseek(file_temp,60,0);
    temp_data1 = fread(file_temp,'single','ieee-be');
    temp_data3 = complex(temp_data1(1:2:end-1),temp_data1(2:2:end));
    

Answer 1

[Walter Roberson]

You attempt to open 45C.fid/fid but 45C.fid does not exist as a folder -- existing folder is 45temps.fid and 45meas.fid

You should be doing

filename = strcat(num2str(temps(ii)),'meas.fid/fid');
[file_temp, msg] = fopen(filename);
if file_temp < 0
    warning('failed to open %s because %s', filename, msg);
    continue
end