Selecting specific elements from a matrix all at once

Question

Is there a way I can select a bunch of prespecified elements all at once from a matrix? Specifically, suppose I have the following matrix:

      58        59             


        

Answer 1

A solution to your specific situation would be to select the sub-matrix and use the diag function:

R> diag(x[-ncol(x),-1])
[1] 3.772139 3.755554 5.999409 3.810169 3.796884