How to change the directory in the middle of a code

Dear All MATLAB Users :-)

I have a critical question whose answer will save much time for me. Well basically the answer to my question will increase my ability of running as many as calculations I need during my sleep hours :-)

Assume on my desktop I have 4 folders ( directories ). Each of them is containing of many text files. The names of these directories are 1,2,3 and 4 respectively.

Now I have a code (m-file) located in each of these sub directories. Obviously once the code is run, all calculation will be performed on the files within that directory. What I basically seek for is a way to change the directory address after calculations for the files located in folder 1 finish. As a result, by running my code once, all of the folders will be covered one after another.

    % THE CODE START RUNNING WITHIN THE DIRECTORY 1 
    for k = 1:50   % NUMBER OF TEXT FILES IN THE FIRST DIRECTORY
    filename = sprintf('%d.txt',k);
    A = load(filename); 
    % doing some calculations
    print the output for k.txt
    end

    % THIS IS WHAT i WANT : Change the directory to the second one and again start running the code for the text files in the second folder.
     for k = 1:10
    filename = sprintf('%d.txt',k);
    A = load(filename); 
    % doing some calculations
    print the output for k.txt
    end

Thank you in advanced. Best, HRJ

Answer 1

[Image Analyst]

Try it this way:

topLevelFolder = 'C:/myData/whatever'; % Forward slashes works with Windows too!
for f = 1 : 4
  % Get the name of this folder.
  thisFolder = sprintf('topLevelFolder/%d', f);
  % See if it actually exists
  if ~isdir(thisFolder)
    errorMessage = sprintf('Error: The following folder does not exist:\n%s', thisFolder);
    uiwait(warndlg(errorMessage));
    continue;
  end
  % Get a list of the .mat files in thisFolder.
  filePattern = fullfile(thisFolder, '*.mat');
  matFiles = dir(filePattern);
  for k = 1:length(matFiles)
    baseFileName = matFiles(k).name;
    fullFileName = fullfile(thisFolder, baseFileName);
    fprintf(1, 'Now reading %s\n', fullFileName);
    % Read it in
    storedStructure = load(fullFileName); 
    % Do some operations.
  end
end

[Homayoon]

Dear Friend,

It does not work out. Maybe I was not clear in stating the question. Well Again I have 4 folders in a Toplevel folder. ( I am using your terminology). Each of these subfolders contains of a mat file. basically this mat file is doing some operations and calculations on the text files in the subfolder. I am looking for writing a code which should locate in my toplevel folder as you pointed out. the code will start from subfolder 1, read the mat file in that folder, then run the mat file for that folder ( this is critical ). Finally it goes to the other subfolder. Please note that the calculation and analysis are clearly laid down in matfiles. Also the output files are supposed to be dumped out in the subfolder associated to the mat file.

[Homayoon]

well unfortunately i always receive such an error message :

The following folder does not exist:topLevelFolder

[Walter Roberson]

The line

  thisFolder = sprintf('topLevelFolder/%d', f);

should have been

thisFolder = fullfile(topLevelFolder, sprintf('%d', f));