[R] xyplot (lattice): colours of lines

[Umberto Maggiore]

It works. However, now I get another odd result: in some plots there are
straight lines connecting the end of a line with the beginning of another 
one.

On Wednesday 04 February 2004 04:03, Umberto Maggiore wrote:
>Using data from a multicenter study with a parallel-group design comparing
>two treatments, I plotted each subject's time change of X after stratifying
>for center:
>
>xyplot(X ~ time | center, type="l", panel=panel.superpose, groups=subject)
>
>Now I want these lines to take different colours according to the variable
>"treatment". Any help?

Umm, you should already have lines colored differently by different
'subject's. Do you want to further differentiate by treatment ?

If that's so, there's probably no good way. You could try creating a new
factor combining subject and treatment and use that as the groups argument,
e.g.,

factor(paste(as.character(subject), as.character(treatment), sep = "/"))

Deepayan