MATLAB indexing question

Question

I have a matrix, for example

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

and a vector of size 1x3 which specifies which element in each row is the one I\

Answer 1

First of all, the indexes in Matlab go from top to bottom.
So in your case A[1] = 1 , A[2] = 4 , A[3] = 7

That said, it would be easier to work on A' , because its a bit more trivial.

B = A';

B((vector + [0:2].* 3))