[R] ggplot2, density barplot and geom_point layer

[hadley wickham]

Because of the way you've constructed the plot with qplot, you need to use:

myPlot + geom_point(
 data=medians,
 aes(x=med,shape=cut, y=0),
 size=2.5,
)

Hadley

On Wed, Apr 7, 2010 at 5:11 AM, Johannes Graumann
<johannes_graumann at web.de> wrote:
> Hi,
>
> Please consider the example below. How can I manage to overlay the points
> the way I want in the second case?
>
> Thanks, Joh
>
> library(ggplot2)
>
> # Modify data to match "real" case
> myDiamonds <- diamonds
> myDiamonds[["clarity"]] <- as.character(myDiamonds[["clarity"]])
> myDiamonds[myDiamonds[["clarity"]]=="I1","clarity"] <- 1
> myDiamonds[myDiamonds[["clarity"]]=="SI2","clarity"] <- 2
> myDiamonds[myDiamonds[["clarity"]]=="SI1","clarity"] <- 3
> myDiamonds[myDiamonds[["clarity"]]=="VS2","clarity"] <- 4
> myDiamonds[myDiamonds[["clarity"]]=="VS1","clarity"] <- 5
> myDiamonds[myDiamonds[["clarity"]]=="VVS2","clarity"] <- 6
> myDiamonds[myDiamonds[["clarity"]]=="VVS1","clarity"] <- 7
> myDiamonds[myDiamonds[["clarity"]]=="IF","clarity"] <- 8
> myDiamonds[["clarity"]] <- as.numeric(myDiamonds[["clarity"]])
>
> # Calculate medians
> medians <- ddply(
>  myDiamonds,
>  .(cut),
>  summarize,
>  med=median(clarity, na.rm=TRUE)
> )
>
> # Works
> myPlot <- qplot(
>  factor(clarity),
>  data=myDiamonds,
>  fill=cut,
>  geom="bar",
>  position="dodge"
> )
>
> myPlot +
> geom_point(
>  data=medians,
>  aes(x=med,shape=cut),
>  y=0,
>  size=2.5,
> )
>
> # Doesn't work - I want density rather than count
> myPlot <-qplot(
>  factor(clarity),
>  y=..count../sum(..count..),
>  data=myDiamonds,
>  fill=cut,
>  geom="bar",
>  position="dodge"
> )
>
> myPlot +
> geom_point(
>  data=medians,
>  aes(x=med,shape=cut),
>  y=0,
>  size=2.5,
> )
>
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>



-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/