[R] Get the indices of non-zero entries of a sparse matrix in R

[G FANG]

Hi,

I am trying to get the indices of non-zero entries of a sparse matrix in R

     s    r d
1 1089 3772 1
2 1109  190 1
3 1109 2460 1
4 1109 3071 1
5 1109 3618 1
6 1109   38 1

I found that the following can create a sparse matrix,

library(Matrix)
Y <- sparseMatrix(s,r,x=d)

but have not idea and did not find online how to convert a sparse
matrix back to three columns efficiently, i.e. get the indices of
non-zero entries of a sparse matrix.

In matlab, the find function can do this efficiently, I am wondering
is there a similar one in R?

Please advice. Thanks!

--gang