MATLAB: Find rows of two matricies (of different sizes) based on matching element of one column

sorting matching matrices

Given two matrices A[1000×4] and B[500×4] 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!

Best Answer

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),:)
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