[R] changing point style in xyplots depending on groups

[Thomas von Känel]

hi,
i've got the following and would like to set the point style for A, B 
and C myself (eg pch=1, 6 and 16)

library(lattice)
df <- data.frame(x  = log(c(1, 0.5 ,0.2 ,0.12 ,0.06, 1, 0.5 ,0.2, 
0.12,0.06, 1, 0.5 ,0.2 ,0.12,0.06)),
        y  = c(1, 2, 5, 14, 24, 51, 50, 50, 49, 54, 100, 101, 103, 97, 95),
        gr = c('A','A','A','A','A','B','B','B','B','B','C','C','C','C','C'))
xyplot(df$y~df$x,groups=df$gr)

thanks in advance for any help
Tom von Känel
Human Genetics
Uni Berne