In this tutorial, we will learn how to highlight a select boxplot using ggplot2 in R. By highlighting a select boxplot with specific color, we can easily divert the attention to it.
Let us first load the packages needed. We will use Palmer Penguins dataset to make boxplots.
library(tidyverse) library(palmerpenguins) theme_set(theme_bw(16))
Our data looks like this.
penguins |> head() # A tibble: 6 × 8 species island bill_length_mm bill_depth_mm flipper_length_mm body_mass_g <fct> <fct> <dbl> <dbl> <int> <int> 1 Adelie Torgersen 39.1 18.7 181 3750 2 Adelie Torgersen 39.5 17.4 186 3800 3 Adelie Torgersen 40.3 18 195 3250 4 Adelie Torgersen NA NA NA NA 5 Adelie Torgersen 36.7 19.3 193 3450 6 Adelie Torgersen 39.3 20.6 190 3650 # ℹ 2 more variables: sex <fct>, year <int>
Here is a simple boxplot with species on x-axis and body mass of penguins on y-axis.
penguins |>
ggplot(aes(species, body_mass_g))+
geom_boxplot()+
labs(title="How to highlight select boxplot")
ggsave("how_to_highlight_select_boxplot.png")
How to highlight select boxplot in ggplot2
In order to highlight one of the boxplots, we first need to create a new variable that defines which boxplot needs to be highlighted. In the example below we aim to highlight Gentoo species as it has large body mass among the three penguin species.
By naively adding the highlight variable either as fill or color, we can add color to the boxplot.
penguins |>
mutate(highlight = ifelse(species == "Gentoo", "Highlighted", "Normal")) %>%
ggplot(aes(species, body_mass_g, fill=highlight))+
geom_boxplot()+
labs(title="How to highlight select boxplot")
ggsave("highlight_select_boxplot_1.png")
Unfortunately it also adds colors to other boxplots as well not just the one we wanted to highlight.
We can get around this problem by manually specifying the color we want to highlight the box plot. IN the example below, we manually set color using scale_fill_manual() function such that the box plot we want to highlight is blue and the rest are white.
penguins |>
mutate(highlight = ifelse(species == "Gentoo", "Highlighted", "Normal")) %>%
ggplot(aes(species, body_mass_g, fill=highlight))+
geom_boxplot()+
scale_fill_manual(values = c("steelblue", "white")) +
theme(legend.position = "none")+
labs(title="How to highlight select boxplot")
ggsave("highlight_select_boxplot_with_specific_color.png")
