R help - Mar 2010 - ggplot2: Adding points to a density plot

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

Hi:

Try this:

library(ggplot2)
movmed <- ddply(movies, .(decade), summarise, med = median(rating))
m + geom_point(data = movmed, aes(x = med), y = 0, size = 2)

HTH,
Dennis

On Wed, Mar 31, 2010 at 4:46 AM, Johannes Graumann
<johannes_graumann@web.de
> wrote:
> 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
>
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