How to replace elements of a matrix with the scaled identity?

Question

Shikhar Shah 2019-12-9

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https://ww2.mathworks.cn/matlabcentral/answers/495742-how-to-replace-elements-of-a-matrix-with-the-scaled-identity

评论： Shikhar Shah 2019-12-9

I have some arbitrary square matrix, for example:

A = [ 1 2 3; 4 5 6; 7 8 9 ];

I would like to replace each element with its scalar value multiplied by the identity of some size n. For example, taking n=2, I want to get:

B = [ 1 0 2 0 3 0;

0 1 0 2 0 3;

4 0 5 0 6 0;

0 4 0 5 0 6;

7 0 8 0 9 0;

0 7 0 8 0 9 ];

Since the size n is constant, the matrix B is guaranteed to have consistent dimensions. Is there a quick way to do this without having to loop over the elements of A and find the corresponding indices of B to place the identity?

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Answer 1

Matt J 2019-12-9

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https://ww2.mathworks.cn/matlabcentral/answers/495742-how-to-replace-elements-of-a-matrix-with-the-scaled-identity#answer_405591

在 MATLAB Online 中打开

B=kron(A,eye(n))

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Shikhar Shah 2019-12-9

This makes a lot of sense. It is useful that I can use any matrix for the second argument of kron(). Thank you so much for your quick and simple answer!

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