Draw ggplot2 Plot with Two Different Continuous Color Scales in R (Example)

In this article you’ll learn how to use two different color ranges in a ggplot2 plot in R.

The table of content is structured as follows:

Let’s start right away:

Creation of Example Data

The first step is to construct some data that we can use in the examples later on:

data1 <- data.frame(x1 = rnorm(500),    # Create first example data frame
                    y1 = rnorm(500))
head(data1)                             # Print head of first example data frame

data2 <- data.frame(x2 = runif(500),    # Create second example data frame
                    y2 = runif(500))
head(data2)                             # Print head of second example data frame

The output of the previous R programming syntax is shown in Tables 1 and 2: As you can see, we have created two different data frames, each consisting of two randomly distributed numeric variables.

Let’s draw these data!

Example: Draw ggplot2 Plot with Two Different Color Scales Using ggnewscale Package

This example explains how to create a ggplot2 plot of two data sets where each data set has its own continuous color range.

As a first step, we have to install and load the ggplot2 package:

install.packages("ggplot2")             # Install ggplot2 package
library("ggplot2")                      # Load ggplot2 package

Next, we also have to install and load the ggnewscale package:

install.packages("ggnewscale")          # Install ggnewscale package
library("ggnewscale")                   # Load ggnewscale

The ggnewscale package provides the new_scale_color function. This function can be used to create a new color scale.

Consider the R programming syntax below:

ggplot() +                              # Draw ggplot2 plot with two color scales
  geom_point(data = data1, aes(x = x1, y = y1, color = y1)) +
  scale_color_gradient(low = "green", high = "blue") +
  new_scale_color() + 
  geom_point(data = data2, aes(x = x2, y = y2, color = y2)) +
  scale_color_gradient(low = "yellow", high = "red")

In Figure 1 you can see that we have managed to create a ggplot2 scatterplot by running the previous R programming code.

The data of the first data set has a color scale ranging from green to blue, and the data of the second data set has a color scale ranging from yellow to red.

The two color ranges have been specified by the scale_color_gradient function, and the new_scale_color function has been used to tell R that we wanted to start a new color scale.

Looks great! 🙂

Video & Further Resources

I have recently published a video on my YouTube channel, which illustrates the R syntax of this tutorial. You can find the video below.

Furthermore, you may want to read the related tutorials which I have published on Statistics Globe. I have published numerous articles on topics such as ggplot2, groups, and lines:

• Draw Plot with Two Y-Axes
• Add Different Line to Each Facet of ggplot2 Plot
• Draw Two ggplot2 Boxplots on Same X-Axis Position
• Set Color by Group in ggplot2 Plot
• Draw ggplot2 Plot with Two Y-Axes in R
• R Graphics Gallery
• Introduction to R

Summary: At this point you should have learned how to use separate color scales in a continuous ggplot2 plot in the R programming language. In case you have any further questions, let me know in the comments section.