submatrix(a, r1, c1, r2, c2)
Returns a submatrix of matrix a with corner entries (r1,c1) and (r2,c2).
See also matrix row column
Example
a = ( 3, 5, 7, 8 ; 3, 4, 7,-4 ; 2, 4, -1, 1 ; 1, 2, -3, -7 )
3 5 7 8
3 4 7 -4
2 4 -1 1
1 2 -3 -7
submatrix( a, 2, 2, 4, 3 )
4 7
4 -1
2 -3