Set Color by Group in ggplot2 Plot in R (4 Examples)

On this page, I’ll show how to specify different group colors in a ggplot2 graph in the R programming language.

The content of the post looks like this:

Let’s dig in:

Example Data, Packages & Default Plot

As a first step, we’ll need to construct some data that we can use in the examples later on:

set.seed(68117534)              # Set random seed
data <- data.frame(x = 1:15,    # Create example data frame
                   y = c(runif(15, 0, 2),
                         runif(15, 2, 6),
                         runif(15, 3, 4),
                         runif(15, 1, 3)),
                   group = rep(LETTERS[1:4], each = 15))
head(data)                      # Print head of example data frame

Table 1 shows the first six rows of our example data: it is also shown that the data contains three columns.

For the examples of this tutorial, I’ll also need to install and load the ggplot2 package to RStudio:

install.packages("ggplot2")     # Install & load ggplot2 package
library("ggplot2")

As a next step, we can plot our data without colors:

ggplot(data,                    # Draw ggplot2 plot without colors
       aes(x = x,
           y = y,
           group = group)) +
  geom_line() +
  geom_point()

By executing the previously shown R programming syntax, we have drawn Figure 1, i.e. a ggplot2 line and point graphic without any colors.

Example 1: Modify Colors of Single Geom by Group

Example 1 shows how to adjust the colors in a ggplot2 plot by group for a single geom.

In this specific example, we are changing the line colors of our plot:

ggplot(data,                    # Change colors of lines by group
       aes(x = x,
           y = y,
           group = group)) +
  geom_line(aes(col = group)) +
  geom_point()

Figure 2 shows the output of the previous syntax: We have adjusted the line colors. However, the color of the points has been kept the same.

Example 2: Modify Colors of All Geoms by Group

It is also possible to change all colors according to the groups in a data set.

To achieve this, we have to specify the col argument within the aesthetics of the ggplot function:

ggplot(data,                    # Change colors of lines & points by group
       aes(x = x,
           y = y,
           col = group)) +
  geom_line() +
  geom_point()

As shown in Figure 3, the previous code has created a new ggplot2 plot where all colors have been changed by group.

Example 3: Using Manual Color Codes by Group

In this example, I’ll demonstrate how to set manual color codes for each group in a ggplot2 graphic.

For this task, we have to use the scale_color_manual function as shown below. Within this function, we can set a different hex color code for each group:

ggplot(data,                    # Specify colors manually
       aes(x = x,
           y = y,
           col = group)) +
  geom_line() +
  geom_point() +
  scale_color_manual(values = c("#ca7dcc",
                                "#1b98e0",
                                "#353436",
                                "#02e302"))

Example 4: Modify Fill Colors of Boxplots by Group

Until now, we have changed the colors in a ggplot2 line and point graph. This example illustrates how to modify the colors of a boxplot graphic.

For this, we can use the fill argument within the aesthetics of the ggplot function:

ggplot(data,                    # Change colors of boxplots
       aes(y = y,
           fill = group)) +
  geom_boxplot()

By executing the previous code, we have created Figure 5, i.e. several boxplots side-by-side where each box has a different fill color.

Video, Further Resources & Summary

Have a look at the following video which I have published on my YouTube channel. I explain the examples of this article in the video.

Furthermore, you might have a look at the other tutorials on my website.

• Change Fill and Border Color of ggplot2 Plot
• Set Axis Limits of ggplot2 Facet Plot
• Control Line Color & Type in ggplot2 Plot Legend
• Change Theme Color in ggplot2 Plot in R
• Change Continuous Color Range in ggplot2 Plot
• Plots in R
• Introduction to R

To summarize: You have learned in this article how to set certain group colors in a ggplot2 graphic in the R programming language. In case you have any further questions, don’t hesitate to kindly let me know in the comments section.