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How to multiply values to specific elements in a matrix?

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Emmanuel
Emmanuel el 19 de Nov. de 2016
Respondida: Roger Stafford el 20 de Nov. de 2016
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!

Respuestas (2)

the cyclist
the cyclist el 19 de Nov. de 2016
Editada: the cyclist el 19 de Nov. de 2016
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 el 20 de Nov. de 2016
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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