[R] ggplot2, density barplot and geom_point layer

[Johannes Graumann]

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,
)