MATLAB: Multiplying mmN matrix internally

matrix manipulation

I have a matrix A with dimensions 2*2*N, and I would like to multiply each 2*2 'slice' of the matrix together to end up with a final 2*2 matrix. I've tried using prod but I haven't had much luck. Is there a better way, or a particular syntax to use? Thanks!

Best Answer

   prod

performs element-wise multiplication.

If you want matrix multiplication, you can use something like :

A = rand(2,2,2);
res = A(:,:,1);
for i = 2:size(A,3)
  res = res*A(:,:,i);
end

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MATLAB: Wrong dimensions on a 3D array

%the below needs R2020b or later
re_arranged = permute(Matrix, [2 3 1]);
filtered = pagetimes(re_arranged, filter_matrix);

The result will be 51 x 51 x 72.

For earlier releases, there is a File Exchange contribution to do page-wise multiplication. Or you can loop:

re_arranged = permute(Matrix, [2 3 1]);
filtered = zeros(size(re_arranged));
for P = 1 : size(re_arranged,3)
  filtered(:,:,P) = pagetimes(re_arranged(:,:,P), filter_matrix);
end

The permute is not strictly necessary. You could skip it and use

filtered = zeros(size(Matrix));
n = size(Matrix,2);
for P = 1 : size(Matrix,1)
    filtered(P, :, :) = reshape( reshape(Matrix(P,:,:), [n, n]) * filter_matrix, [1, n, n]);
end

The output would be 72 x 51 x 51

MATLAB: Dynamic pressure m m

Use the plot() function, the xlabel() and ylabel() functions, the text() function, and the legend() function.

Best Answer

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