How to multiply values to specific elements in a matrix?

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Emmanuel
Emmanuel 2016-11-19
回答： Roger Stafford 2016-11-20
I have a matrix
A=[ 1 0 0 0;
0 1 0 0;
1 0 0 0;
0 0 0 1 ]
I want to multiply an array B= [1,5,7,8] to wherever 1's are in matrix A. Resultant matrix is:
A = [1 0 0 0;
0 5 0 0 ;
7 0 0 0;
0 0 0 8]
How can I do it in vectorized form? Please note that number of ones in input matrix A will always equal the length of array B
Thanks!

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回答（2 个）

the cyclist
the cyclist 2016-11-19
编辑：the cyclist 2016-11-19
In MATLAB 2016b (and presumably later yet-to-be-released versions), you can just write
A.*B'
In earlier versions, you need to use bsxfun:
bsxfun(@times,A,B')
Roger Stafford
Roger Stafford 2016-11-20
Assuming the number of ones in A is equal to the length of B,
At = A.’;
At(At==1) = B;
A = At.’;

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