How to multiply values to specific elements in a matrix?

Question

0 个投票

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;
5 0 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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Answer 1

the cyclist 2016-11-19

编辑：the cyclist 2016-11-19

0 个投票

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')

Answer 2

Roger Stafford 2016-11-20

0 个投票

Assuming the number of ones in A is equal to the length of B,

   At = A.’;
   At(At==1) = B;
   A = At.’;