Manually draw boxplot using ggplot

February 9, 2022

I think my question is very similar to this one, the only difference being that I’d love to use ggplot (and the answer with ggplot was missing a tiny bit of detail). I have data like this:

show<-structure(list(Median = c(20, 39, 21, 52, 45.5, 24, 36, 20, 134, 
27, 44, 43), IQR = c(4, 74, 28, 51.5, 73.5, 18, 47.5, 26.5, 189.5, 
46, 54, 61), FirstQuartile = c(`25%` = 19, `25%` = 24, `25%` = 12, 
`25%` = 30.5, `25%` = 36.5, `25%` = 18, `25%` = 16.5, `25%` = 13, 
`25%` = 53.5, `25%` = 15, `25%` = 24.5, `25%` = 27), ThirdQuartile = c(`75%` = 23, 
`75%` = 98, `75%` = 40, `75%` = 82, `75%` = 110, `75%` = 36, 
`75%` = 64, `75%` = 39.5, `75%` = 243, `75%` = 61, `75%` = 78.5, 
`75%` = 88), Group = c("Program Director", "Editor", "Everyone", 
"Board Director", "Board Director", "Program Director", "Editor", 
"Everyone", "Board Director", "Everyone", "Editor", "Program Director"
), Decade = c("1980's", "1980's", "1980's", "1980's", "1990's", 
"1990's", "1990's", "1990's", "2000's", "2000's", "2000's", "2000's"
)), row.names = c(NA, -12L), class = c("tbl_df", "tbl", "data.frame"
))

And I would like to draw a graph like this:

With "group" as the color, instead of "fellowship". The problem is, that graph was drawn from "complete" data (with 800ish rows), and I clearly only have summary data above. I realize it won’t be able to draw outliers but that is ok. Any help would be appreciated! I’m specifically struggling with how I would draw the ymin/max and the edges of the notch. Thank you

>Solution :

You can use geom_boxplot() with stat = "identity" and fill in the five boxplot numbers as aesthetics.

library(ggplot2)

# show <- structure(...) # omitted for previty

ggplot(show, aes(Decade, fill = Group)) +
  geom_boxplot(
    stat = "identity",
    aes(lower  = FirstQuartile,
        upper  = ThirdQuartile,
        middle = Median,
        ymin   = FirstQuartile - 1.5 * IQR,
        ymax   = ThirdQuartile + 1.5 * IQR)
  )

As pointed out by jpsmith in the comments below, if you have information about the data extrema or the data domain, you can limit the whiskers as follows:

# Dummy values assuming data is >= 0 up to infinity
show$min <- 0
show$max <- Inf

ggplot(show, aes(Decade, fill = Group)) +
  geom_boxplot(
    stat = "identity",
    aes(lower  = FirstQuartile,
        upper  = ThirdQuartile,
        middle = Median,
        ymin   = pmax(FirstQuartile - 1.5 * IQR, min),
        ymax   = pmin(ThirdQuartile + 1.5 * IQR, max))
  )