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

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Shikhar Shah
Shikhar Shah on 9 Dec 2019
Commented: Shikhar Shah on 9 Dec 2019
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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Accepted Answer

Matt J
Matt J on 9 Dec 2019
B=kron(A,eye(n))

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Shikhar Shah
Shikhar Shah on 9 Dec 2019
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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