[R] Adding mean line to a lattice density plot

[K. Elo]

Hi!

I have used the following command:

densityplot(~PV1CIV, groups=SGENDER, data=ISGFINC2,
   lwd=2, col=1, lty=c(1,2), pch=c("+","o"),
   key=list(text=list(lab=levels(ISGFINC2$SGENDER), col=1),
   space="bottom", columns=2, border=T, lines=T, lwd=2,
   lty=c(1,2), col=1), ref=T, plot.points=F)

to produce a lattice density plot presenting the distribution of 
achievment points grouped by the gender of the respondents.

Now, in order to clarify the difference between boys and girls, I would 
like to add two vertical lines: one for the mean of boys, the other for 
the mean of girls. How could I do this (I have tried to use the function 
'panel.abline', but could not figure out how to define the correct 
x-axis point (using 'v=mean(PV1CIV[ SGENDER==1 ])' as a parameter is not 
working...).

Thanks in advance,
Kimmo