Add text over bars in ggplot2 when using fill aesthetic

Question

I would like to place * above some bars in my bar plot. This would be straightforward if I was not using the fill aesthetic, but with it, I cannot figure out how to place stars over the bars, rather than the x-axis ticks.

I have tried to use geom_text , and was unsuccessful. I see that I can add them manually using annotate , but this is an inelegant solution.

Here is a minimal example of the dataset and plot I would like to add * to:

df <- data.frame(age = c('year1', 'year1', 'year2', 'year2'),
                 category = c('cat1', 'cat2', 'cat1', 'cat2'),
                 value = 1:4,
                 star = c("", "*", "", "")
)

g <- ggplot(data = df, aes(category, proportion, fill = age))
g <- g + geom_bar(stat = "identity", position = position_dodge())
g

How can I add the * from my data set in the star column over the corresponding bar?

Answer 1

I would suggest this approach using geom_text() in dodge style:

library(ggplot2)
#Data
df <- data.frame(age = c('year1', 'year1', 'year2', 'year2'),
                 category = c('cat1', 'cat2', 'cat1', 'cat2'),
                 value = 1:4,
                 star = c("", "*", "", "")
)
#Plot
g <- ggplot(data = df, aes(category, value, fill = age,label=star))
g <- g + geom_bar(stat = "identity", position = position_dodge())
g <- g + geom_text(position = position_dodge(0.9),vjust=-0.5)
g

Output:

Let me know if that is what you wanted.