[R] distinguish regression lines in grouped, black and white lattice xyplot

[Katharina May]

Hi,

I've got the following problem which I cannot think of a solution right now:

if got a lattice xyplot in black and white and a grouping variable
with many (more than 8
values) and I plot it as regression lines (type="r"), just like this
one (not reproducable but that's
I guess not the point here):

xyplot(log(AGWB) ~ log(BM_roots), data=sub_agwb_data, groups=species,
type="r", lty=c(1:6),panel=allo.panel.5)

The problem is that I've got 26 different values for the grouping
variable species and only 6 default values for the line type
lty (and according to the par {graphics} help page customizable to up
to 8 different line types).

Does anybody have any idea how these 26 different lines can be made
distinguishable from each other without the use
of colors?

Thanks,

         Katharina