Access matrix location on one matrix with the data location on another matrix

I have two matrix say A & B if I have data stored in A and the data location of desired values in B how could I access Values of matrix A who are located at locations B.

Answer 1

[Chinmay Anand]

In case if A and B are vectors ,( 1 x n ) matrices

A(B)  % It will give the values of A at indexes B

[Rohan Mehta]

I want to keep values of A on location B as it is and set all other to zero.

Thanks for the help....

[Chinmay Anand]

idx = setdiff(1:length(A),B); % indexes which are not in B
A(idx) = 0;              

[Rohan Mehta]

Thank you so much this works !!!

Answer 2

[madhan ravi]

Probably you want:

idx = setdiff(1:numel(A),B);
A(idx) = 0;

[Rohan Mehta]

yes Exactly what I wanted

[madhan ravi]

Beware this method works even if A is a matrix more than 1 dimension unlike the other.