Activity: Functions and data frames

Creating a plot

The code below creates side-by-side boxplots to show the distribution of carat for each different cut in the diamonds data:

library(tidyverse)

diamonds |>
  ggplot(aes(x = cut, y = carat)) +
  geom_boxplot() +
  theme_bw() +
  labs(title = "Distribution of carat by cut in the diamonds data")

1. Adapting this code, write a function called group_boxplot which allows you to make side-by-side boxplots, given a data frame and the two variables to plot. Here are some examples of the function in action:

library(palmerpenguins)

group_boxplot(diamonds, cut, carat)

group_boxplot(diamonds, carat, cut)

group_boxplot(penguins, species, bill_depth_mm)

Solution:

group_boxplot <- function(df, x, y) {
  label <- rlang::englue("Distribution of {{y}} by {{x}} in the {{df}} data")
  
  df |>
    ggplot(aes(x = {{ x }}, y = {{ y }})) +
    geom_boxplot() + 
    theme_bw() +
    labs(title = label)
}

Hint: For titling the plots, see the examples with the englue function in Section 25.4.3 of R for Data Science (2nd edition).