Importing text files using uigetfile

I'm attempting to import some data from a text file. When I use the Import Data tool and then use the generate script function it works fine. (snippet below)

filename = 'C:\Documents and Settings\gavinbr\Desktop\Muirake\test files\NL_001_OCT_Lp _0001_0001.rnd';
delimiter = ',';
startRow = 3;

formatSpec = '%*s%*s%*s%*s%*s%*s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%[^\n\r]';

fileID = fopen(filename,'r');

dataArray = textscan(fileID, formatSpec, 'Delimiter', delimiter, 'HeaderLines' ,startRow-1, 'ReturnOnError', false);

However I wish to replace the first line with:

[filename,pathname] = uigetfile('*.rnd','Select the rnd file to process','Multiselect','on');

So I can select the files I wish to process each time and select more than one file each time. However it returns the following error:

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

Error in importscript (line 33)
dataArray = textscan(fileID, formatSpec, 'Delimiter', delimiter, 'HeaderLines' ,startRow-1, 'ReturnOnError', false);

Does anyone know how I can get around this?

Thanks in advance

Answer 1

[Azzi Abdelmalek]

Check the value of fileID

fileID = fopen(filename,'r')

If fileID is equal to -1, that means you can't open the file for many reasons, maybe the file doesn't exist.

[Gavin Brown]

Thanks for the quick response. fileID = 3

[Gavin Brown]

Apologies I was reading off the wrong script. fileID is equal to -1. Any ideas what any of they reasons would be?

Thanks again

[Stephen23]

There are many reasons why a file cannot be opened: it does not exist (is the path correct?), it is already open (in MATLAB, or another program?), it is blocked somehow by the OS...

You could try using this syntax defined in the fopen documentation, and see if what the message says:

"[fileID,errmsg] = fopen(__) additionally returns a system-dependent error message if fopen fails to open the file"

[Gavin Brown]

When I use that it returns with "No such file or directory". I don't really understand how it can't exist if I selected it. I'm sort of new to this. Will it have something to do with the pathname?

Cheers

[Stephen23]

Probably you are only providing the filename to fopen, and not the path as well. If you do not supply any path information, then fopen will only look in the current directory. Consider the difference:

fid = fopen('my_work.txt','rt');

looks for a file called my_work.txt located in the current directory. Whereas

strP = 'C:\Users\Anna\Results';
strF = 'my_work.txt';
fid = fopen(fullfile(strP,strF),'rt');

also provides the directory location. You should look at Jan Simon's answer, which shows you how to use this in a complete example, but basciyll you need to do this:

[filename,pathname] = uigetfile(...);
str = fullfile(pathname,filename);
fid = fopen(str,'rt');
... ETC

Answer 2

[Jan]

[filename, pathname] = uigetfile('*.rnd', 'Select the rnd file to process', 'Multiselect', 'on');
if isequal(filename, 0)
  disp('User aborted reading of files.');
  return;
end

for k = 1:length(filename)
  aFile = fullfile(pathname, filename{k});
  % Now perform the operation with this file. E.g. show its name:
  disp(aFile);

    fid = fopen(aFile, 'r');
    if fid < 0
      error('Cannot open file: %s', filename);
    end
    ...
  end