r is na code example
Example 1: if not na in r
> which( !is.na(p), arr.ind=TRUE)
row col
[1,] 1 2
[2,] 1 3
[3,] 2 4
[4,] 4 5
[5,] 2 7
Example 2: if not na in r
> apply(p, 1, function(x) which(!is.na(x)) )
[[1]]
[1] 2 3
[[2]]
[1] 4 7
[[3]]
integer(0)
[[4]]
[1] 5
[[5]]
integer(0)