Matlab提取3D矩阵对角线的有效方法 [英] matlab efficient way to extract diagonals of a 3D matrix

问题描述

我想将3D矩阵(下面的Sigma)的对角线提取到另一个3D矩阵(下面的Sigma2).

I want to extract diagonals of a 3D matrix (Sigma below) into another 3D matrix (Sigma2 below).

Sigma = repmat(magic(4),1,1,3);
Sigma2 = nan(1,4,3);
for i=1:3
    Sigma2(1,:,i) = diag(Sigma(:,:,i));
end

有没有更有效的方法?

推荐答案

可以.如果将Sigma整形为矩阵，则选择3D矩阵的对角线现在可以从矩阵中选择行.

You can. If you reshape Sigma to a matrix, selecting the diagonal of the 3D matrix is now selecting rows from a matrix.

Sigma3=reshape(Sigma,[],size(Sigma,3));
Selector=diag(true(size(Sigma,1),1));
Sigma2=Sigma3(Selector(:),:);
%Sigma2=permute(Sigma2,[3,1,2]) %optional last step to get a result with the same dimensions.

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