lookup table as a matrix instead of an array

I have a matrix square R which contains the relation ship (distances) between numbers. Elements in R is uint8 and the size is 256 x 256.

Let say I have two other matrix A and B of same size now. Now I want to generate Matrix C which is extracted from R. In other words, looking the values of A and B in R and putting them in C.

For example

C ( 5, 5 ) = R(A(5,5), B(5,5));

I can't do it using intlut as it is for any array. How can we do it if we have matrix ?

Answer 1

[Jan]

See sub2ind.

index = sub2ind(size(R), A(:), B(:));
C = reshape(R(index), size(A));