[R] truncating a data frame based on a function

[Faheem Mitha]

On Fri, 21 Sep 2007, Greg Snow wrote:

> Look at the subset function (?subset), it may do what you want.

This looks useful. Thanks. However, how can I write an expression 
selecting certain rows (subset argument) in the case of a matrix? when it 
does not have named columns? The documentation does not have examples of 
this.
                                                            Faheem.