How to add a number of observations per group and use group mean in ggplot2 boxplot?
boxplot, ggplot2, r
Solution
Is this anything like what you're after? With `stat_summary`, as requested:
# function for number of observations
give.n <- function(x){
return(c(y = median(x)*1.05, label = length(x)))
# experiment with the multiplier to find the perfect position
}
# function for mean labels
mean.n <- function(x){
return(c(y = median(x)*0.97, label = round(mean(x),2)))
# experiment with the multiplier to find the perfect position
}
# plot
ggplot(mtcars, aes(factor(cyl), mpg, label=rownames(mtcars))) +
geom_boxplot(fill = "grey80", colour = "#3366FF") +
stat_summary(fun.data = give.n, geom = "text", fun.y = median) +
stat_summary(fun.data = mean.n, geom = "text", fun.y = mean, colour = "red")
Black number is number of observations, red number is mean value. joran's answer shows you how to put the numbers at the top of the boxes
hat-tip: https://stackoverflow.com/a/3483657/1036500
Problem
I am doing a basic boxplot where `y=age` and `x=Patient groups` ``` age <- ggplot(data, aes(factor(group2), age)) + ylim(15, 80) age + geom_boxplot(fill = "grey80", colour = "#3366FF") ``` I was hoping you could help me out with a few things: 1) Is it possible to include a number of observations per group above each group boxplot (but NOT on the X axis where my group labels are) without having to do this in paint :)? I have tried using: ``` age + annotate("text", x = "CON", y = 60, label = "25") ``` where `CON` is the 1st group and `y = 60` is ~ just above the boxplot for this group. However, the command didn't work. I assume it has something to do that it reads `x` as a continuous rather than a categorical variable. 2) Also although there are plenty of questions about using the mean rather than the median for the boxplots, I still haven`t found a code that works for me? 3) On the same matter is there a way you could include the mean group stat in the boxplot? Perhaps using ``` age + stat_summary(fun.y=mean, colour="red", geom="point") ``` which however only includes a dot of where the mean lies. Or again using ``` age + annotate("text", x = "CON", y = 30, label = "30") ``` where `CON` is the 1st group and `y = 30` is ~ the group age mean. Knowing how flexible and rich `ggplot2` syntax is I was hoping that there is a more elegant way of using the real stats output rather than `annotate`. Any suggestions/links would be much appreciated! Thanks!!