how can i take average of matrices in a cell?

Hi, i have a cell array X{16*12} in which each element of cell X is a 3d array. now I want to take the average of all the matrices in the row which will result in another cell array Y{1,12} (each element of Y cell array consist of 3d array). can anyone please help me with this.

thank you

[Bob Thompson]

It is possible to use the mean() function with a 3D array, but if you want a single value average of the entire array you're going to need to take the average multiple times, as mean only calculates along one dimension at a time.

Doing this inside a cell array should just be a matter of indexing.

[Joseph]

Hi, Thanks for your comment.I think you are talking about taking the mean of each 3D array inside the cell, however, by averaging I meant summing all the matrices in the first column of the cell array X and dividing by the number of matrices (i.e. X{1,1}+X{2,1}+...+X{16,1}/16). note that X{1,1}, ... are 3d arrays.

sorry if my question wasn't clear enough.

[Bob Thompson]

Ok, that's definitely a bit different. Are you looking to do element averaging, or the entire matrices? Based on your indexing I'm going to guess you want elements.

That shouldn't really be too difficult to do with a couple for loops, just something like the following.

for dir1 = 1:size(cellmat,1); % Loop through rows of matrices
   for dir2 = 1:size(cellmat,2); % Loop through columns of matrices
      for dir3 = 1:size(cellmat,3); % Loop through sheets of matrices
        summation = 0; % Reset summation value to 0 for next element
        for numbermats = 1:size(greatercellmatrix,1) % Loop through all matrices in first column
             summation = summation + greatercellsmatrix{numbermats,1}(dir1,dir2,dir3); % Add next matrix element
        end % Numbermats for
        resultsmat(dir1,dir2,dir3) = summation/numbermats; % Record average of sum
      end % Sheets
   end % Columns
end % Rows

Others are welcome to chime in if there is a better way of doing this than for loops, I'll admit I have a bit of a tendency to get stuck on them simply because I know them relatively well, so other functions that do things like this tend to escape me.

[Joseph]

Thank you so much Bob, even though your answer wasn't that I wanted, but it gave me the idea how to do it. i was looking for the averaging of the entire matrices in the for each column of the cell X(16,12). which will result in another cell like resultcell(1,12) in which each element of resultcell is a 3D array. something like following.

   for numbercol = 1:size(X,2)

        summation = 0; % Reset summation value to 0 for next element

        for numbermats = 1:size(X,1) % Loop through all matrices in first 
        column

             summation = summation + X{numbermats,numbercol}; % Add next 
           matrix element

        end % Numbermats for

        resultcell{1,numbercol} = summation/numbermats; % save avarage of each column of the cell X in the cell resultcell

end;

[Bob Thompson]

Cool, glad I could help. I deliberately avoided putting the answer into a cell matrix since I figured it would just be numbers and a cell matrix of numbers is just extra complicated, but you do what you need to.

Answer 1

[Andrei Bobrov]

A - your cell array

one variant

[m,n,k] = size(A{1});
[h,l] = size(A);
A1 = reshape(cat(3,A{:}),m,n,k,h,l);
out = squeeze(num2cell(mean(A1,4),1:3))';

[Joseph]

Thanks for your Answer Andrei, this works too.