find rows of two matricies (of different sizes) based on matching element of one column

Given two matrices A[1000x4] and B[500x4] what is the fastest way in MATLAB to extract the complete rows of A which share the same element values in column 4 as B does?

for example if,

A=[1 2 3 7; 
   2 6 9 1; 
   8 3 4 8] and 
B=[9 2 5 1; 
   6 2 1 5; 
   3 6 6 8].

What is the most efficient way to create a new array

C=[2 6 9 1;  
   8 3 4 8],

having the rows of A with same element in column 4 as B does?

Thanks!

Answer 1

[Image Analyst]

Try ismember():

A=[1 2 3 7; 
   2 6 9 1; 
   8 3 4 8]  
B=[9 2 5 1; 
   6 2 1 5; 
   3 6 6 8]

[ia, ib] = ismember(A(:,4), B(:, 4))
C = A(find(ib),:)

[Adam]

Perfect! That's the function I needed :)

Answer 2

[James Tursa]

Caution, untested:

k = ismember(A(:,4),B(:,4));
C = A(k,:);