annotate grouped boxplot in ggplot - add number of observations below boxplot

Question

I want to add the number of observations below each boxplot (as in the figure- no need for the red square). :) However, I don't know how to annotate this type of boxplot (see figure below).multiple boxplot annotate number of observations

Does anyone know how to do it?

This is the code that I used to plot this figure.

ggplot(data=MIOT1, aes(stage, time, fill=resp)) +
geom_boxplot(color= "black", lwd=0.3) +
stat_summary(fun.y=mean, geom="point", shape=0, size=1, colour="black", position=position_dodge(width=0.75)) +
scale_fill_manual(values=c("grey25", "grey50", "grey67")) +
annotation_custom(mygrobA) +
scale_y_continuous(limits=c(-10,124)) +
theme(panel.grid.major = element_blank(),
    panel.grid.minor = element_blank(),
    strip.background = element_rect(colour="black"),
    panel.border = element_rect(colour = "black", fill="transparent")) +
xlab(bquote(' ')) +
ylab(bquote('Minimum Consecutive Time (s)')) +
labs(title="SATIATION\n") +
theme(axis.title.y = element_text(colour="black",size=10,face="bold"),
    axis.text.x = element_text(colour="black",size=8, face="plain"),
    axis.text.y = element_text(colour="black",size=8, face="plain"),  
    axis.title.x = element_text(colour="black",size=10,face="bold")) +  
theme(panel.background = element_rect(fill = "white")) +
theme(plot.title = element_text(lineheight=.8, size=10, face="bold")) +
theme(legend.title=element_blank(), legend.key = element_rect(fill = NA, colour = NA)) +
theme(legend.position="none") +
theme(legend.background = element_rect(fill=NA)) +
theme(plot.margin = unit(c(.25,.25,.0,.0), "cm"))<i>

EXAMPLE DATA MIOT1 is a numeric variable (y-axis), and I am considering two grouping factors (development stage- x axis) and the response (unresponsive, coastal, lagoon).

Something like

stage  resp  time
pre       U      100
pre       U      80
pre       U       50
pre       C       20
flex       U      80
flex       U       90
flex       C       10
flex        C      20
post      U        40
post      U        30
post      U        60
post       C      80
post      C       100
post       L       50
post       L       40

Thank you! Pedro

Please provide us some sample data that we can work with. Right now we have no idea what MIOT1 is which makes it hard for us to replicate your problem. A dput(MIOT1) would be helpful. For more information check out: stackoverflow.com/questions/5963269/… — Mike H.

eipi10 eipi10 · Accepted Answer · 2016-05-19T17:44:12

Here's a simple example of how to do it, using the built-in mtcars data frame:

ggplot(mtcars, aes(factor(cyl), mpg)) + 
  geom_boxplot() +
  geom_text(stat="count", aes(label=..count..), y=min(mtcars$mpg)- 0.6)

In your case, it will be something like

ggplot(data=MIOT1, aes(stage, time, fill=resp)) +
  geom_boxplot(color= "black", lwd=0.3) +
  geom_text(stat="count", aes(label=..count..), y=min(MIOT1$time))

where you may have to adjust the y location of the text labels and you might also need to adjust the range of the y-axis to make room for the labels.

UPDATE: I was able to reproduce the error you reported, but I'm not sure how to fix it. Instead, you can pre-summarize the data and then add it to the plot. Here's an example:

library(dplyr)

# Get counts by desired grouping variables
counts = mtcars %>% group_by(cyl, am) %>% tally


ggplot(mtcars, aes(factor(cyl), mpg, fill=factor(am))) + 
  geom_boxplot(position=position_dodge(0.9)) +
  geom_text(data=counts, aes(label=n, y=min(mtcars$mpg) - 0.6),
        position=position_dodge(0.9))

annotate grouped boxplot in ggplot - add number of observations below boxplot

2 Answers