[R] extract cells by columns/rows from matrix

[Nicolas Gutierrez]

hi All,

I have a matrix Ufi (x by y)

   1  2  3  4  5
1 0  0  0  0  3
2 0  0  0  9  0
3 0  2  0  0  3
4 0  0  1  0  0
5 0  1  0  0  0

And I need the x and y "coordinates" of those cells with maximum values:

First:

x=4; y=2  (Value=9)

Second:

x=5; y=3  (value=3)

Any help?
THANKS!

Nic