MATLAB: How to combine several matrices

Question

Elements of matrix B are row numbers of matrix A. The row number of matrix A start from 0. Matrix A has several zero rows.

produce matrix C:

when an element of matrix B refer to a zero row of matrix A, the row of matrix B should be replaced with zero.

For instance, I would like to produce Matrix C.

 A =
 0.0   0.0
 0.4   0.8
 0.0   0.0
 0.2   0.6
 B= 
 1  0
 0  2 
 3  1
 2  3
 2  1
 C=
 0  0
 0  0 
 3  1
 0  0
 0  0

Answer 1

It's not clear from your description what happens when one of the column of a row of A is 0 and the other isn't.

This is one way to produce the output you want

C = B;
C(any(A(B+1) == 0, 2), :) = 0

Note that the output of

C = B;
C(A(B+1) == 0) = 0

would have made more sense to me.