On Jul 6, 2010, at 3:46 PM, G FANG wrote:
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?
Yes there is, and it was reasonably easy to find with the help systems
starting from the Matrix help page.
?sparseMatrix
summary(Y)
--
David Winsemius, MD
West Hartford, CT
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