[R] Dotplot (package Hmisc) with groups: colours and symbols

[E Hofstadler]

Hello all,

This question concerns the function Dotplot from the Hmisc package.

My aim is to compare values between groups in each panel of the
Dotplot, with the values of different groups clearly distinguishable
by different symbols. All lines and symbols should be coloured in
black.

Before adding the panel function to the Dotplot, the groups behaved as
desired and were marked by different symbols, but the error bands were
blue instead of black. After adding the panel function and changing
the trellis colour settings, the error bars are now black, but now the
groups are suddenly marked by the same rather than different symbols.
I've tried several ways to change the group symbols but to no avail.

## set CI lines to black
t1 = trellis.par.get("plot.line")
t1$col <- "black"
trellis.par.set("plot.line",t1)

## load example data
require(lattice)
data(barley)

## example plot (problem: groups marked by the same symbol)

require(Hmisc)
Dotplot(site~Cbind(yield, yield+5, yield-5)|variety, groups=year,
data=barley, pch=c(1,2), col="black",
        panel=function(x,y){
            panel.Dotplot(x,y,col="black")})
Key()




What am I doing wrong?

Many thanks in advance.
Esther