[R-sig-eco] How do I convert a matrix from abundant into presence/absence data?

[Cory Redman]

I am sure there is any easy solution to this, but due to my
monkey-level understanding of R, I need some help and can't seem to
find the answer to my question via the web.

I have been successful in importing an abundance dataset (taxa = rows,
sample sites = columns) into R, but I want to rerun some analyses by
converting this dataset into presence/absence data, How do I do this?

Cheers,
   Cory