Getting error while loading .mat file from many directory

I have main directory named'data' and sub directories (r1,r2,r3...). In each sub directory, I have several folders(r1_0.05,r1_0.10,...) and .mat file as shown in figure below. I am using below code to load .mat file from each sub-directory and do some operation.

close all; clear all; clc;
project_dir = pwd();                                                    %or give a particular directory name
mainDirContents = dir(project_dir);
mainDirContents(~[mainDirContents.isdir]) = [];                         %remove non-folders
mask = ismember( {mainDirContents.name}, {'.', '..'} );
mainDirContents(mask) = [];                                             %remove . and .. folders
num_subfolder = length(mainDirContents);
nod=1;
for subfold_idx = 1 : num_subfolder
subfolder_name = mainDirContents(subfold_idx).name;
this_folder = fullfile( project_dir, subfolder_name );
  matContents =  dir( fullfile(this_folder, '*.mat') );
  this_mat = fullfile( this_folder, matContents(subfold_idx).name );
  loadmatfile=load(this_mat);
%     do operation for each .mat file of the current folder 
end

But I am getting error as Index exceeds matrix dimensions.

Error in Untitled5 (line 14) this_mat = fullfile( this_folder, matContents(subfold_idx).name );

Any idea to solve this is highly appreciated. Thank you.

Answer 1

[Stephen23]

Your indexing is incorrect, and you need another loop.

Basically you are looping over the directories, but then you try to use the directory iteration variable to indexing into the file structure. Here is the relevant part of your code:

for subfold_idx = 1 : num_subfolder
    ...
    matContents =  dir( fullfile(this_folder, '*.mat') );
    ...   matContents(subfold_idx).name
end

For example, imagine if there are two directories, then subfold_idx will have values 1 and 2. But if there is only one .mat file in the second directory, then it will be an error to try to use subfold_idx with value 2 ! (because there is no second file).

You need to add another loop of for the files.

[sam moor]

.mat file is included in each sub-directory(i.e. r1, r2, r3...). for first subfold_idx=1 it runs great but when subfold_idx=2, it gives me error. I don't know where to add loop for the files

[Stephen23]

@sam moor: put the "file" loop inside the "folder" loop. Use the internet and search for "nested loops".

[sam moor]

got it thank you very much