Adding labels in ggplot for summary statistics - r

Question

About 18 months ago, this helpful exchange appeared, with code to show how to produce a plot of median along with interquartile ranges. Here's the code:
ggplot(data = diamonds) +
geom_pointrange(mapping = aes(x = cut, y = depth),
stat = "summary",
fun.ymin = function(z) {quantile(z,0.25)},
fun.ymax = function(z) {quantile(z,0.75)},
fun.y = median)
Producing this plot:
What I'd wonder is how to add labels for the median and IQ ranges, and how to format the bar (color, alpha, etc). I tried calling the plot as an object to see if there were objects within I could then use to call format functions, but nothing was obvious when I looked at it in the r Studio IDE.
Is this even doable? I know I can do a boxplot but that would have to include min/max. I'd like to produce boxplots with just mean/median and IQs.

Answer 1

You can change the formating like you would any ggplot layer, see the docs for Vertical intervals: lines, crossbars & errorbars in this case. An example of this is the following:
library(ggplot2)
ggplot(data = diamonds) +
geom_pointrange(mapping = aes(x = cut, y = depth),
stat = "summary",
fun.ymin = function(z) {quantile(z,0.25)},
fun.ymax = function(z) {quantile(z,0.75)},
fun.y = median,
size = 4, # <- adjusts size
colour = "red", # <- adjusts colour
alpha = .3) # <- adjusts transparency
If you want to control formatting for the points and lines individually you need to do as #camille suggests and pre-process your data as geom_pointrange() draws a single graphical object so the points and lines are one in the same.
I would suggest something like this:
library(dplyr)
library(ggplot2)
diamonds %>%
group_by(cut) %>%
summarise(median = median(depth),
lq = quantile(depth, 0.25),
uq = quantile(depth, 0.75)) %>%
ggplot(aes(cut, median)) +
geom_linerange(aes(ymin=lq, ymax=uq), size = 4, colour = "blue", alpha = .4) +
geom_point(size = 10, colour = "red", alpha = .8)