MATLAB: Mean of many changing “for loop” 3D matrices

3d matrices

Hi,
I have 200 3D matrices with same dimensions. I'd like to create one 3d matrix that would contain mean of my 200 matrices by elements → (1,1,1) mean of 200 positions in my 3D matrices and so on …
Here's my code:
for tt = 1:200;
      M =      ...         (tt)                                            loads the 3D data
  end
  mean()
Can you help me please?
Thanks.

Best Answer

Well, you could do that (store in a 4D array, that is) but that requires memory for all 200 at once and there's no need when computing a mean to have all the data at once...just accumulate the totals and then divide after the loop is finished...
    M = spm_read_vols(spm_vol(files(1).name));  % read the first into accumulator array
    for tt = 2:200
       M=M+spm_read_vols(spm_vol(files(tt).name));  % accumulate the total
    end
    M=M/200;    % average
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