How to Create a ggplot Plot with Two Y-Axes in R (Example Code)

On this page you’ll learn how to draw a plot with two y-axes using the ggplot2 package in R programming.

Preparing the Example

data(iris)                                         # Loading example data
head(iris)
#   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
# 1          5.1         3.5          1.4         0.2  setosa
# 2          4.9         3.0          1.4         0.2  setosa
# 3          4.7         3.2          1.3         0.2  setosa
# 4          4.6         3.1          1.5         0.2  setosa
# 5          5.0         3.6          1.4         0.2  setosa
# 6          5.4         3.9          1.7         0.4  setosa

Example: Creating ggplot2 Plot of Iris Data with Two Y-Axes

First, we have to install and load the ggplot2 add-on package:

install.packages("ggplot2")                        # Install ggplot2 package
library("ggplot2")                                 # Load ggplot2 package
ggplot(iris, aes(1:nrow(iris), Sepal.Length)) +    # Drawing iris data in ggplot2 plot
  geom_point() + 
  scale_y_continuous(
    "Sepal.Length in Centimeters", 
    sec.axis = sec_axis(~ . * 10, name = "Sepal.Length in Millimeters")
  )

r graph figure 1 create ggplot two y axes

Related Articles

Here, you may find some additional resources on topics such as graphics in r, ggplot2, and variables:

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