Bubble charts

Graph info

Should I use this graph?

This graph requires:

✅ three numeric (continuous) variables

Description

Bubble graphs display relationships between three numeric (continuous) variables.

The position on the x and y axis illustrates the relationship between the first two variables, and the size of the point (i.e., the bubble) conveys the numeric value of the third.

Getting set up

Packages

PACKAGES:

Install packages.

Code

install.packages("palmerpenguins")
library(palmerpenguins)
library(ggplot2)

Data

DATA:

Artwork by @allison_horst

The penguins data

Code

penguins <- palmerpenguins::penguins
glimpse(penguins)

Rows: 344
Columns: 8
$ species           <fct> Adelie, Adelie, Adelie, Adelie, Adelie, Adelie, Adel…
$ island            <fct> Torgersen, Torgersen, Torgersen, Torgersen, Torgerse…
$ bill_length_mm    <dbl> 39.1, 39.5, 40.3, NA, 36.7, 39.3, 38.9, 39.2, 34.1, …
$ bill_depth_mm     <dbl> 18.7, 17.4, 18.0, NA, 19.3, 20.6, 17.8, 19.6, 18.1, …
$ flipper_length_mm <int> 181, 186, 195, NA, 193, 190, 181, 195, 193, 190, 186…
$ body_mass_g       <int> 3750, 3800, 3250, NA, 3450, 3650, 3625, 4675, 3475, …
$ sex               <fct> male, female, female, NA, female, male, female, male…
$ year              <int> 2007, 2007, 2007, 2007, 2007, 2007, 2007, 2007, 2007…

The grammar

Code

CODE:

Create labels with labs()

Map bill_length_mm to x axis

Map flipper_length_mm to y axis

Map body_mass_g to size

Set alpha to 1/3

Add scale_size(), set the range to c(0.1, 10) and name to "Body Mass (g)"

Move the legend to the bottom of the graph with theme(legend.position = "bottom")

Code

labs_bubble <- labs(
  title = "Bill Length vs. Flipper Length",
  x = "Bill Length (mm)", y = "Flipper length (mm)", 
  size = "Body Mass (g)")

ggp2_bubble <- penguins |> 
  ggplot(
    aes(x = bill_length_mm, y = flipper_length_mm)) + 
  geom_point(aes(size = body_mass_g), alpha = 1/3) + 
  scale_size(range = c(.1, 10), 
             name = "Body Mass (g)") + 
  theme(legend.position = "bottom")

ggp2_bubble + 
  labs_bubble

Graph

GRAPH: