MATLAB: Using a matrix values to point to another matrix rows&cols

Question

Hi,

So matrix 1 is a 102×2 matrix full of x and y coordinates. Matrix 2 is a 102×3 matrix, where the second column values refer to which row in matrix one has relevant information. For all the values in matrix two column 2, I need the information in that row in matrix 1 put into a third matrix.

simply:

M1 = x y M2 = row.no M3 = xy of row

1 2 3 2 1

1 3 1 1 2

2 1 2 1 3

I've been trying variants of

%into every row in column 1 = for every col 2 in M2, the row in M1;
M3(:,1) = M1(M2(:,2),:);

But every change I make seems to not work, so I think I'm doing it totally wrong? I could possibly do it with a for loop but I'm still not sure how to use a value in a matrix to indicate the row in another matrix. Any advice would be much appreciated!

Answer 1

M3 = M1(M2(:,2),:);