MATLAB 3D数组的交集

Question

I have two 3d arrays:

A(:,:,1) = [1 2 3; 4 5 6; 7 8 9];
A(:,:,2) = [1 0 0; 0 1 0; 0 0 1];
A(:,:,3) = [3 2 1; 6 5 4; 9 8 7];
...

and

B(:,:,1) = [1 1 1; 2 2 2; 3 3 3];
B(:,:,2) = [1 0 0; 0 1 0; 0 0 1];
B(:,:,3) = [3 3 3; 2 2 2; 1 1 1];
...

They both consist of 3x3 matrices and their third dimensions are very large. I want to obtain the array of matrices that exist in both arrays. I am doing it in a for loop by comparing element-wise (matrix-wise). It takes a very long time, so I am looking for an easier way (or an existing function) to do the same.

Thanks!

Answer 1

Collapse the first two dimensions into one and transpose, so that matrices of the 3D array become rows of a matrix. That way you can use intersect(...,'rows') . Finally, transpose back and reshape back:

[m, n, p] = size(A);
result = intersect(reshape(A, [], p).', reshape(B, [], p).', 'rows');
result = reshape(result.', m, n, []);