重塑矩阵从3d到2d保持行 [英] Reshape matrix from 3d to 2d keeping rows

问题描述

我正在将3d矩阵转换为2d矩阵。这是形状变换：[n x m x o] - > [n * o x m]。

I am transforming a 3d matrix into a 2d matrix. This is the shape transformation: [n x m x o] -> [n*o x m].

矩阵的元素与行有关。因此，需要在结果矩阵中具有相同的行。

The elements of the matrices are row-related. Thus, it is required to have the same rows in the resulting matrix.

A = rand(2,2,3);

这样做：

C = reshape(A, 2*3, 2);

未将行保留在A中。

所以我这样做：

B = zeros(size(A,1)*size(A,3),size(A,2));
first_indice = 1;
for i = 1:size(A,3)
    B(first_indice:size(A,1)*i,:)=A(:,:,i);
    first_indice = first_indice + size(A,1);
end

是否有更有效的方式可能使用重塑？

Is there a more efficient way maybe using reshape?

非常感谢！

推荐答案

reshape结合了从第一维开始的矩阵元素。因此，解决方案是在重塑之前置换尺寸。在您的情况下，它应如下所示：

reshape combines the matrix elements starting from the first dimension. Thus, the solution would be to permute the dimensions prior to reshaping. In your case it should be as follows:

% A is the input matrix of dimensions (n x m x o).
B = ipermute(A, [1 3 2]);
C = reshape(B, n*o, m);

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