Finding a value of one vector based on the nonzero values of another vector

Given two vectors, how do you determine the value of A where B is 1? In this case, A=[5 4]. How do I do this?

A = [2 5 1 4];
B = [0 1 0 1];

Answer 1

[Arif Hoq]

A = [2 5 1 4];
B = [0 1 0 1];
[I C]=find(B==1);
output=A(C)

output = 1×2

5 4

Answer 2

[Image Analyst]

If B is always guaranteed to be 0 or 1, you can do this

A = [2 5 1 4];
B = [0 1 0 1]; % B is a double here.
A = A(logical(B)) % Need to cast B to logical

A = 1×2

5 4

If B can be anything and you want to get A where B is not equal to zero:

A = [2 5 1 4];
B = [0 23 0 341];
A = A(B ~= 0)

A = 1×2

5 4

[Stephen23]

Using LOGICAL() works in both cases:

A = [2 5 1 4];
B = [0 23 0 341];
A = A(logical(B))

A = 1×2

5 4

Answer 3

[Voss]

A = A(B == 1)