Argument on 2 vectors without using for loop

I have 2 vectors

A=[10 22 31 14 55 16 47 18];
B= [1 2 1 1 1 2 1 2];

I want to make a third vector C which contains values of A for values of B=1; like

C=[10 NaN 31 14 55 NaN 47 NaN]

or

C=[10 31 14 55 47]

I did this using a for loop. Just want to know if this is doable without using for loop as it may save a lot of computation time. (The vectors with me are really really large

for i=1:length (A);
if B(i)==1;
C(i)=A(i)
else C(i)=NaN;
end;
end;

Answer 1

[madhan ravi]

A=[10 22 31 14 55 16 47 18];
B= [1 2 1 1 1 2 1 2];

C=A(B==1)