Adding Tukey's significance letters to boxplot

Question

I'm trying to create a boxplot with ggplot of a count (MedMean) on yaxis and various independent samples (Site_Name) on xaxis.

ggplot(medianlist,aes(x=reorder(Site_Name,MedMean,FUN=median),y=MedMean))+
geom_boxplot()

I want to add Tukey's significance letters to the boxes.

Thanks

ggplot(iris,aes(x=reorder(Species,Petal.Length,FUN = median),y=Petal.Length))+geom_boxplot() — B.Shermeister, Feb 05 '18 at 18:29
This is the same function using the "iris" file. I want to add letters showing significance between species (in this example) — B.Shermeister, Feb 05 '18 at 18:30
Possibly related: https://stackoverflow.com/q/44712185/783245 — Marcus Ritt, Apr 24 '18 at 00:48

score 5 · Accepted Answer · answered Apr 24 '18 at 01:10

Using agricolae::HSD.test you can do

library(dplyr)
library(agricolae)
library(ggplot2)
iris.summarized = iris %>% group_by(Species) %>% summarize(Max.Petal.Length=max(Petal.Length))
hsd=HSD.test(aov(Petal.Length~Species,data=iris), "Species", group=T)
ggplot(iris,aes(x=reorder(Species,Petal.Length,FUN = median),y=Petal.Length))+geom_boxplot()+geom_text(data=iris.summarized,aes(x=Species,y=0.2+Max.Petal.Length,label=hsd$groups$groups),vjust=0)

Adding Tukey's significance letters to boxplot

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