A = [1 2 ; 3 4]

A =

     1     2
     3     4

A([1 2],[2 2])

ans =

     2     2
     4     4

A([2 1],[1 2])

ans =

     3     4
     1     2

A([1 2],[2 2]) = A([2 1],[1 2])

A =

     1     4
     3     2

diary off