[R] xyplot with grid?

[Gav Wood]

Gabor Grothendieck wrote:
> Add the argument
> 
>    type = c("p", "g")
> 
> to your xyplot call.

So what's the easiest way to place a line at x=3 (ala "abline(v=3)") to 
the graph? After calling the xyplot call, the panel.* functions seem to 
work only in device coordinates.

Thanks for the help,

Gav