r - Boxplot show the value of mean

Question

In this boxplot we can see the mean but how can we have also the number value on the plot for every mean of every box plot?

 ggplot(data=PlantGrowth, aes(x=group, y=weight, fill=group)) + geom_boxplot() +
     stat_summary(fun.y=mean, colour="darkred", geom="point", 
                           shape=18, size=3,show_guide = FALSE)

Answer 1

First, you can calculate the group means with aggregate:

means <- aggregate(weight ~  group, PlantGrowth, mean)

This dataset can be used with geom_text:

library(ggplot2)
ggplot(data=PlantGrowth, aes(x=group, y=weight, fill=group)) + geom_boxplot() +
  stat_summary(fun=mean, colour="darkred", geom="point", 
               shape=18, size=3, show.legend=FALSE) + 
  geom_text(data = means, aes(label = weight, y = weight + 0.08))

Here, + 0.08 is used to place the label above the point representing the mean.

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An alternative version without ggplot2:

means <- aggregate(weight ~  group, PlantGrowth, mean)

boxplot(weight ~ group, PlantGrowth)
points(1:3, means$weight, col = "red")
text(1:3, means$weight + 0.08, labels = means$weight)