How to annotate geom_bar above bars?

Question

I'm trying to do a simple plot using ggplot2:

library(ggplot2)

ggplot(diamonds, aes(x = cut, y = depth)) + 
  geom_bar(stat = "identity", color = "blue") +
  facet_wrap(~ color) +
  geom_text(aes(x = cut, y = depth, label = cut, vjust = 0))

How can I annotate this plot so that I get annotations above bars? Now geom_text puts labels at the bottom of the bars, but I want them above these bars.

Answer 1

You can use stat_summary() to calculate position of y values as sum of depth and use geom="text" to add labels. The sum is used because your bars shows the sum of depth values for each cut value.

As suggest by @joran it is better to use stat_summary() instead of geom_bar() to show sums of y values because stat="identity" makes problems due to overplotting of bars and if there will be negative values then bar will start in negative part of plot and end in positive part - result will be not the actual sum of values.

ggplot(diamonds[1:100,], aes(x = cut, y = depth)) + 
  facet_wrap(~ color) + 
  stat_summary(fun.y = sum, geom="bar", fill = "blue", aes(label=cut, vjust = 0)) + 
  stat_summary(fun.y = sum, geom="text", aes(label=cut), vjust = 0) 

You can also precalculate sum of depth values and the you can use geom_bar() with stat="identity" and geom_text().

library(plyr)
diamonds2<-ddply(diamonds,.(cut,color),summarise,depth=sum(depth))

ggplot(diamonds2,aes(x=cut,y=depth))+
  geom_bar(stat="identity",fill="blue")+
  geom_text(aes(label=cut),vjust=0,angle=45,hjust=0)+
  facet_wrap(~color)