[R] finding cols and rows in a matrix

[javier garcia]

Hi
Ive got big matrixes with just few non missing data, and
would like to use or do a funtion to find the index of the row and col of one 
specified value. For example I just have one "1" value in the matrix, and one 
"2" value in the same matrix.

Has anyone an idea about how to extract the rowindex and colindex of the "1" 
value or the "2"?

Thanks