[R] ggplot2: Adding points to a density plot

[Johannes Graumann]

Hi,

Consider something like
> library(ggplot2)
> movies$decade <- round_any(movies$year, 10)
> m <- qplot(rating,data=movies,colour=factor(decade),geom="density")
> m
(modified from "?stat_density").

I'd like to add on the line y=0 a dot for the median of each "decade" 
category (using the same colour coding as the "fill"). I'm failing miserably 
at all my
> m + geom_point
based approaches and would appreciate if someone could show me the ggplot2 
way of achieving this.

Thanks, Joh