How do I concatenate 3D arrays from multiple .mat files?

I have 360 archives.mat, each with a variable 'A', of size 1800x400x1. I would like to concatenate these arrays in the third dimension, ie I would like an 'A1' of size 1800x400x360. For this I tried two things: 1) I used the 'cat' command (as in the code below), but it just saved the last array:

          d=dir('test/*.mat');%test is the name of my directory where these files are stored
          nn=length(d);
          A1=[];
          for ii=1:nn
             eval(['load teste/',d(ii).name]) 
             disp(d(ii).name)
             A1=cat(3,A);
          end

2) I tried to use [], but it only concatenates in the first or second dimension:

         d=dir('test/*.mat');
         nn=length(d);
         A1=[];
         for ii=1:nn
            eval(['load test/',d(ii).name]) 
            disp(d(ii).name)
            A1=[A1;A];
          end

Anyone have any suggestions on how to solve this? Thanks.

[Stephen23]

Note that eval does nothing useful here at all, except to complicate the code and make debugging harder. All you need is:

load(...)

Or even better:

S = load(...)

For example:

S = load(fullfile('test',d(ii).name))

Answer 1

[Walter Roberson]

A1 = cat(3, A1, A);

but you could also use

A1(:,:,ii) = A;

and you could pre-allocated, like

          d=dir('test/*.mat');%test is the name of my directory where these files are stored
          nn=length(d);
          for ii=1:nn
             eval(['load teste/',d(ii).name]) 
             disp(d(ii).name)
             if ii == 1
               A1 = zeros(size(A,1), size(A,2), nn);
             end
             A1(:, :, ii) = A;
          end

However, you should avoid using eval:

          projectdir = 'test';
          d = dir( fullfile(projectdir, '*.mat') );
          nn = length(d);
          for ii=1:nn
             load( fullfile(projectdir, d(ii).name) ) 
             disp(d(ii).name)
             if ii == 1
               A1 = zeros(size(A,1), size(A,2), nn);
             end
             A1(:, :, ii) = A;
          end

and you should avoid using load() without any output:

          projectdir = 'test';
          d = dir( fullfile(projectdir, '*.mat') );
          nn = length(d);
          for ii=1:nn
             datastruct = load( fullfile(projectdir, d(ii).name), 'A' );
             A = datastruct.A; 
             disp(d(ii).name)
             if ii == 1
               A1 = zeros(size(A,1), size(A,2), nn);
             end
             A1(:, :, ii) = A;
          end

[Thaís Fernandes]

Thank you for trying to help! But even doing that I still find the error "Assignment has more non-singleton rhs dimensions than non-singleton subscripts", or something complaining about the different dimensions of the matrices, always after running to the first file.

[Guillaume]

When stating an error: copy/paste the full text of the error message, everything in red. Do not leave it up to us to guess which line gives the error and what the error actually is.

[Thaís Fernandes]

Ok. Thank you. I tried to specify a little more.

[Walter Roberson]

The message suggests that at least one of the files contains 3d data rather than 2d.

[Thaís Fernandes]

I was able to solve this using exactly what @Walter Roberson suggested, but I ended up using 2D arrays and concatenating in the third dimension.

Thank you all for the help !!!

[Walter Roberson]

I thought that was what my code did? What changes did you have to make?

[Daianne Hofig]

I had the same problem, and his code worked super smoothly! Thank you!