[R] Stratifying data with xyplot

[Sebastien Bihorel]

Hi, 

I am a big user/fan of the lattice package for plotting. As far as I know, lattice only offers one method to stratify data within a xyplot panel, using the groups arguments. 
A contrario, the ggplot package allow users to use different variables for coloring, setting the symbols, the line types or the size of symbols. This frequently comes handy.
My question is whether any work has been done in the lattice ecosystem to reproduce this functionality? If so, I would greatly appreciate any pointers to the appropriate package documentation. 

Thank you

Sebastien