How to go through multiple subfolders for operation?

I only can access into one folder and process the data inside that folder. My Code is like this

%Specifying file directory for Ignition delay time 
    IGNfolder = '/home/ali//Curve_Matching_vs_Moments/IDT/test/Test_rig';
    % It checks whether the folder actually exists or not.  Warning message to the user if not.
    if ~isdir(IGNfolder)
      errorMessage = sprintf('Error: The following folder is not found:\n%s', IGNfolder);
      uiwait(warndlg(errorMessage));
      return;
    end
  % To get all the files in that directory and with desired file name pattern.
   Allfiles = dir(fullfile(IGNfolder, '*.txt'));
  allData = [];
  for k = 1:length(Allfiles)
    initialFileName = Allfiles(k).name;
    fullFileName = fullfile(IGNfolder, initialFileName);
.
.
.
end

If i have multiple such kind of folder (Test_rig), How can i access into them one after another ?

For better explaining if i have one folder named 'JSR' which contains subfolders name " '1', '2', '3', '4'......................., 'n' " .

N.B: There are other subfolders also, but i only need to access into subfolders named " '1', '2', '3', '4'......................., 'n' " .

Answer 1

[Stephen23]

"For better explaining if i have one folder named 'JSR' which contains subfolders name '1', '2', '3', '4'......................., 'n' "

P = 'path to directory JSR';
S = dir(fullfile(P,'*'))
X = [S.isdir] & ~cellfun('isempty',regexp({S.name},'^\d+$','once'));
S = natsortfiles(S(X)); % optional: download from FEX.
for k = 1:numel(S)
    F = fullfile(P,S(k).name) % path to subdirectory.
    ... your code
end

You can download natsortfiles here:

https://www.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort

[Mr. 206]

Thanks so much.

It would great help, if you edit my code.

[Stephen23]

"It would great help, if you edit my code. "

Your code does not mention any folder with the name '1', '2', etc., so it is not clear how your code relates to your actual question, or my answer. Also I used dir to identify the subfolder names, so isdir is totally superfluous. Only you can decide if this is suitable for your workflow.

Perhaps this is what you want:

P = 'path to directory JSR';
S = dir(fullfile(P,'*'))
X = [S.isdir] & ~cellfun('isempty',regexp({S.name},'^\d+$','once'));
S = natsortfiles(S(X)); % optional: download from FEX.
for ii = 1:numel(S) % loop over each subfolder.
    T = dir(fullfile(P,S(ii).name,'*.txt'));
    for jj = 1:numel(T) % loop over each file.
        F = fullfile(P,S(ii).name,T(jj).name);
        ... code processing file F.
    end
end

[Mr. 206]

Thank you very much.

That is what i wanted.

Great!!