Grouped scatter plots

Graph info

Should I use this graph?


This graph requires:

✅ two numeric (continuous) variable

✅ a categorical variable

Description

Grouped scatter-plots display the relationships between two continuous variables across a third categorical variable.

The x and y position displays the relationship between the two continuous variables, and color is used to distinguish between the categorical levels.

Getting set up

PACKAGES:

Install packages.

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

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:

Create labels with labs()

Initialize the graph with ggplot() and provide data

Map bill_length_mm to the x axis

Map flipper_length_mm to the y axis

Map species to color inside the geom_point()

Code 
labs_grp_scatter <- labs(
  title = "Bill Length vs. Flipper Length",
  x = "Bill Length (mm)", 
  y = "Flipper length (mm)", 
  color = "Species")

ggp2_grp_scatter <- penguins |> 
  ggplot(
    aes(x = bill_length_mm, 
        y = flipper_length_mm)) + 
  geom_point(aes(color = species)) 

ggp2_grp_scatter + 
  labs_grp_scatter

GRAPH:

Adjust over-plotting with transparency (alpha)