Changing default quantiles (hinges) in boxplot

Question

I've been learning R for the past few months and I've struggled with something that I couldn't figure out.
I have a really simple question, how do I display percentiles 20 and 80 instead of 25 and 75 (or Q1/Q3) in a boxplot while using tidyverse?

I have tried to find documentation about it in the R Graph Gallery and in the tidyverse help and a lot other sites, but I couldn't reproduce. Usually the examples are with only 1 box, but I have a 7 to be shown.

Here is a sample of my data:

dataset <- structure(
  list(
    PM1 = c(0.4, 6.2, 5.1, 7.8, 8, NA, NA, 5.2), 
    PM2 = c(2, 8, 5.6, 8, NA, 6.4, 10.3, 7), 
    PM3 = c(NA, 7.2, 4.8, 4.4, NA, NA, 10.3, 5.9), 
    PM4 = c(1.2, 8.7, 5.4, NA, NA, NA, NA, NA), 
    PM5 = c(3.5, NA, 1.9, 2.2, NA, 3.5, 9.4, 0.3), 
    PM6 = c(1.3, NA, 1.1, NA, NA, 2.8, NA, NA), 
    PM7 = c(NA, NA, NA, 0.4, NA, NA, 8.8, 0.6)), 
  row.names = c(NA, -8L), 
  class = c("tbl_df", "tbl", "data.frame")
)

I can make the boxplot with this different quantiles using qboxplot, here's the code that I used:

library(qboxplot)
dataset %>% 
  qboxplot(
    main = "Dissolved Oxygen",
    probs = c(0.20, 0.50, 0.80),
    ylim = c(0, 12),
    ylab = "mg/L",
    xlab = "Monitoring Points"
  )

I have searched for something similar to probs = c(0.20, 0.50, 0.80) from the qboxplot package in the ggplot2 but I found different approaches that I couldn't reproduce, like here, here and here.

library(tidyverse)
dataset %>% 
  pivot_longer(
    cols = everything(),
    names_to = "monitoring_point",
    values_to = "oxigenio_dissolvido"
  ) %>% 
  ggplot(
    aes(x = monitoring_point,
        y = oxigenio_dissolvido)
  )+
  stat_boxplot(
      geom = "errorbar",
      width = 0.3,
      position = position_dodge(width = 0.65)
    )+
  geom_boxplot()+
  labs(title = "Dissolved Oxygen",
       y = "oxigenio_dissolvido (mg/L)")+
  scale_y_continuous(
      expand = expansion(mult = c(0,0)),
      limits = c(0, 12)
    )+
  theme_bw()+
  theme(
    plot.title = element_text(hjust = 0.5)
  )

I think I'm close to my desired output, but I really didn't get how to change the hinges. Thank you very much in advance for helping me!

maybe this https://stackoverflow.com/questions/69623509/adding-boxplot-outliers-after-specifying-quantiles will help you — AlexB, Oct 26 '22 at 10:18

Tom Clegg · Accepted Answer · 2022-10-26T13:31:11.140

Define the function to draw each element of the box plot:

f <- function(x) {
  r <- quantile(x, probs = c(0.1, 0.2, 0.5, 0.8, 0.9))
  names(r) <- c("ymin", "lower", "middle", "upper", "ymax")
  return(r)
}

Then plot it as a stat_summary()


dataset %>% 
  pivot_longer(
    cols = everything(),
    names_to = "monitoring_point",
    values_to = "oxigenio_dissolvido"
  ) %>% 
  ggplot(aes(monitoring_point,
           oxigenio_dissolvido)) + 
  geom_boxplot() +
  stat_summary(fun.data = f, geom="boxplot")

Code modified from a previous related question

Changing default quantiles (hinges) in boxplot

1 Answers1