Why am I getting an 'Unable to open file.' error with importdata?

Hi,

Patience is requested for the simple question, I haven't used Matlab since undergrad times.

I need to understand how to avoid an error with 'importdata'. Using 'importdata' or 'csvread' I get 'Unable to open file' errors, even when I can see the file being read if I caption 'importdata' with 'eval'.

I tested it with debugger and the filename is resolving correctly. When I use the filename as a string, it works ok. When I use uiimport it works also. Obviously these solutions won't be practical for many repetitions (numreps is in the order of 100s).

Looking at the variable workspace I can see that 'newfile' is actually populated with the correct data.

I am running MATLAB R2011b on OSX 10.8.

for n = 0:numreps
   fle = strcat('batchRun', num2str(n,'%03d'), '_crt.csv');
   %newfile = importdata(fle);
   %newfile = importdata('batchRun000_crt.csv')
   eval('newfile = importdata(fle)');
end;

Thanks in Advance,

[Walter Roberson]

Are you sure you want %04s and not %04d ?

[Angus]

Correct, i just found that error. Have edited the question.

[Jan]

"eval('newfile = importdata(fle)');"?! Why not:

newfile = importdata(fle);

I'd prefer SPRINTF, but this might be a question of taste:

fle = sprintf('batchRun%03d_crt.cvs', n);

[Angus]

See below in your Answer for comments.

Answer 1

[Jan]

In your posted code, thet variable newfile is overwritten in each iteration. Are you sure that all files are existing?

newFile = cell(1, numreps + 1);
for n = 0:numreps
  fle = sprintf('batchRun%03d_crt.cvs', n);
  try
    newFile{n + 1} = importdata(fle);
  catch
    fprintf('Cannot read: %s\n', fle);
    disp(exist(fullfile(cd, fle)))
  end
end

[EDITED] Avoiding errors is better than catching them, so I'd prefer:

folder  = cd;
newFile = cell(1, numreps + 1);
for n = 0:numreps
  fle = fullfile(folder, sprintf('batchRun%03d_crt.cvs', n));
  if exist(fle, 'file') == 2
    newFile{n + 1} = importdata(fle);
  else
    fprintf('Skip missing file: %s\n', fle);
  end
end

[Angus]

Yes, that's true - I didn't include any processing of the file, which was to copy values from specific lines of 'newfile' to another array, in a new row for each iteration of the loop. I missed this out for brevity, and because the code was working.

Thanks Jan - sprintf worked without raising an error. note: I used 'eval' because this way i got the array imported before the error was raised.

[Jan]

@Angus: You cannot cheat Matlab to import a file inspite of an error using eval().

[Angus]

Maybe not, but for some reason it worked on my configuration with 'eval'. I didn't understand why and chased it down with the debugger and saw the variable be updated before an error was raised. However I needed to continue the assignment and didn't pursue further.

Answer 2

[Angus]

update: I got around this by putting in a try/catch statement which did nothing with the error since the data was being imported to the variable. I still don't know why the error occurs.