how to extract the diagonal entries out of a matrix

[Edward]

Hi,

For example, there is a matrix like:

[ 1 2 3 4 
  5 6 7 8 
  3 5 7 0
  4 8 2 5 ]
and I want to get the diagonal elements out of the matrix and make into a vector: [ 1 6 7 5]  .

I know I could write some lines to do it, but I just want to know if there is a built-in function can do the job. Thank you.

--
Edward