ggplot boxplot but with boxes extending to 5th and 95th percentiles

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

stat_summary() allows the user to specify the ymin, lower, middle, upper, and ymax. By simply modifying the original code to make the ymin = lower, and ymax = upper, the plot will extend the lower end of the boxes to the specified percentile.

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

## original with whiskers extending to the 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")))

## modified range with boxes extending to the 5th and 95th (no whiskers)
p + stat_summary(geom = "boxplot", 
             fun.data = function(x) setNames(quantile(x, c(0.05, 0.05, 0.5, 0.95, 0.95)), 
                                             c("ymin", "lower", "middle", "upper", "ymax")))