[R-sig-Geo] Question - Efficient matrix element selection

[Juan Jose Downes]

Dear all,

I am working in a code whose goal is the
selection of matrix rows according to their 
column values.

The problem is that the matrix I am working
with has 60 columns per 6.000.000 rows, so
I am looking for the most efficient way to
perform the selection.

Any hint about that?

Thanks in advance

Juan