[R] auto.key = TRUE in xyplot() draws max. 7 groups

[Edzer J. Pebesma]

In the example below:

library(lattice)
n = 100
a = rnorm(n)
b = rnorm(n)
c = sample(c(1:7), n, repl=TRUE)
xyplot(a ~ b, groups = c, auto.key = TRUE)
c = sample(c(1:8), n, repl=TRUE)
xyplot(a ~ b, groups = c, auto.key = TRUE)

a key is drawn for the first, but not for the
second graph. I suppose it has to do with the
number of groups. If not a bug, maybe
this should go into the documentation?
--
Edzer