I want to write code in matlab to access files inside folders

the code I want to write is need two for loop, one to access folders inside one folder, and the second for loop to access the files inside those folders. the folder name is RO_ISR2 and type of files are mat.I use MATLAB R2022b

this is the code which I wrote it:

Folder = 'C:\Users\97152\Downloads\copy code\RO_ISR2 (2)\RO_ISR2';

FileList = dir((Folder));

FileList = FileList(3:end);

for k = 1:numel(FileList)

folder=FileList(k).name;

folderpath=fullfile(Folder,folder);

matfiles=dir(fullfile(folderpath,'*.mat'));

p=dir('*.mat');

for j=1:numel(p)

data=load(p(j).name);

File = fullfile(FileList(k).folder, FileList(k).name);

Data{k} = readtable(File);

end

[Stephen23]

Note that this code

FileList = FileList(3:end);

is a buggy attempt to remove dot directory names:

https://www.mathworks.com/matlabcentral/answers/484430-using-struct-dir-selpath-what-do-and-mean-as-struct-name#answer_395754

https://www.mathworks.com/matlabcentral/answers/40949-omitting-pointers-when-listing-folder-contents#answer_50568

https://www.mathworks.com/matlabcentral/answers/13978-list-of-files-sorting#answer_19278

As Walter Roberson wrote in that last link: "In short: if your code assumes that '.' and '..' are the first two entries in a directory, your code has a bug (even in MS Windows). If your code assumes that directory entries are returned in any sorted order, your code has a bug (in all OS.)"

The recommended approaches are ISMEMBER or SETDIFF or similar.

Answer 1

[Shaik mohammed ghouse basha]

Hi @hanoo,

I understand you have a Main Folder and there are sub folders in it. Each sub folder has files in it and you want one loop to iterate through sub folders and other loop to iterate files in each sub folder.

I have tried to replicate your code in my system and it works fine. Here is the code:

Folder = 'C:\Users\gshaik\Downloads\copy code\RO_ISR2 (2)\RO_ISR2';

cd(Folder);  %cd into the main folder

Folders_List = dir(Folder);  %get List of all sub folders
Folders_List = Folders_List(3:end);  % Removed the initial .         .. 


for i = 1:numel(Folders_List)  %Iterate through all sub folders

    Folder_Inside = Folders_List(i).name; %get name of each sub folder 
    
    Folder_Inside_Path = fullfile(Folder, Folder_Inside)  %get full path of sub folder
    
    mFiles=dir(fullfile(Folder_Inside_Path,'*.m'))   %get all .m files in the sub folder
   
    cd(Folder_Inside_Path);       %cd into the sub folder in order to access the files in second loop

    for j = 1:numel(mFiles)  %iterate through all the .m files
        data = load(mFiles(j).name);  %perofrom any operation on the .m you want
    end

end

Here I used .m files to test this code you can .mat or any type of files you want to use.

One key thing is before iterating into the .mat files in each sub folder it is important to cd into the sub folder in order to access files of sub folder hence I used the command: cd(Folder_Inside_Path);

[t]

Thank you so much for your answer, it is working now

[Stephen23]

"% Removed the initial . .. "

No, that is actually a common yet buggy attempt to remove the dot directory names. For more information:

https://www.mathworks.com/matlabcentral/answers/484430-using-struct-dir-selpath-what-do-and-mean-as-struct-name#answer_395754

https://www.mathworks.com/matlabcentral/answers/40949-omitting-pointers-when-listing-folder-contents#answer_50568

https://www.mathworks.com/matlabcentral/answers/13978-list-of-files-sorting#answer_19278

As Walter Roberson wrote in that last link: "In short: if your code assumes that '.' and '..' are the first two entries in a directory, your code has a bug (even in MS Windows). If your code assumes that directory entries are returned in any sorted order, your code has a bug (in all OS.)"

Avoid calling CD inside code like that (it is slow and makes debugging harder). It is much better to use absolute/relative filenames. All MATLAB functions which import/export file data accept absolute/relative filenames.

Rather than nested loops a simpler approach is to simply use DIR with appropriate wildcards.

Note that .m files are code, not data that can be LOADed.

So simpler, more robust code which fixes those bugs would be e.g.:

P = 'C:\Users\gshaik\Downloads\copy code\RO_ISR2 (2)\RO_ISR2';
S = dir(fullfile(P,'*','*.mat'));
for k = 1:numel(S)
    F = fullfile(S(k).folder,S(k).name);
    S(k).data = load(F);
end

[t]

I will edit the code, thank you