How to add a number of observations per group and use group mean in ggplot2 boxplot?

Question

I am doing a basic boxplot where y=age and x=Patient groups

age <- ggplot(data, aes(factor(group2), age))  + ylim(15, 80) 
age         


        

Answer 1

I think this is what you're looking for maybe?

myboxplot <- ddply(mtcars,
                    .(cyl),
                    summarise,
                    min = min(mpg),
                    q1 = quantile(mpg,0.25),
                    med = median(mpg),
                    q3 = quantile(mpg,0.75),
                    max= max(mpg),
                    lab = length(cyl))
ggplot(myboxplot, aes(x = factor(cyl))) + 
    geom_boxplot(aes(lower = q1, upper = q3, middle = med, ymin = min, ymax = max), stat = "identity") + 
    geom_text(aes(y = max,label = lab),vjust = 0)

I just realized I mistakenly used the median when you were asking about the mean, but you can obviously use whatever function for the middle aesthetic you please.