MATLAB: How to extract elements of a multi-dimensional array using the rows of another array as the indices? (more detail in the question)

Question

Suppose I have an array

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

I have another array, say,

B = [1,3;2,1;3,2]

I would like to have an output of

C = [A(1,3);A(2,1);A(3,2)]

or in other words

C = [A(B(1,1),B(1,2));A(B(2,1),B(2,2));A(B(3,1),B(3,2))]

which is supposed to be

C = [3;4;8]

I was hoping to do this without resorting to a loop such as

for i = 1:3
  C(i) = A(B(i,1),B(i,2))
end

I mistakenly tried

C = A(B(:,1),B(:,2))

but clearly that won't work.

Loops will be too time-consuming for me at this point so I was looking for a way to do it at once.

Any help will be appreciated.

Thanks!

Answer 1

A = [1,2,3;4,5,6;7,8,9]
B = [1,3;2,1;3,2]
C = A(sub2ind(size(A),B(:,1),B(:,2))