ggplot boxplot 但框扩展到第 5 个和第 95 个百分位数

Question

I would like to have a boxplot summarize the distribution of some underlying data, but in place of the whiskers extending to the 5th and 95th, I would like the boxes to extend to the 5th and 95th.

Standard boxplot with outliers and whiskers removed:

library("ggplot2")
p <- ggplot(mtcars, aes(factor(cyl), mpg))
p + geom_boxplot(outlier.shape = NA, coef = 0)

Boxplot with whiskers at 5th and 95th:

p + stat_summary(geom = "boxplot", 
                 fun.data = function(x) setNames(quantile(x, c(0.05, 0.25, 0.5, 0.75, 0.95)), 
                                                 c("ymin", "lower", "middle", "upper", "ymax")))

But what I really want is the boxes (no whiskers) to extend to the 5th and 95th, so a combination of both of these modifications. Is there a way to specify the box-generating function in stat_summary() ?

Answer 1

This might be a slightly "hacky" method of doing it, but the easiest way might be to just use geom_segment for each cylinder class. This will allow you to specify the width of the boxplot and the values that you want the boxplot to reach. But you could then play around with aes() and also add in a median line using stat_summary() if desired.

library(ggplot2)
p <- ggplot(mtcars, aes(factor(cyl), mpg))
p + geom_segment(aes(x = 4, xend = 4, y = quantile(subset(mtcars, mtcars$cyl==4)$mpg,0.95), yend = quantile(subset(mtcars, mtcars$cyl==4)$mpg, 0.05)), color = 'firebrick1', lwd = 28)