Change Axis Labels of Boxplot in R (2 Examples)
In this article, I’ll illustrate how to rename the x-axis labels of a boxplot in the R programming language.
The article will consist of these contents:
So let’s start right away…
Example Data & Default Plot
The following data will be used as basement for this R programming tutorial:
set.seed(9736425) # Create example data data <- data.frame(x1 = rnorm(100), x2 = rnorm(100, 2), x3 = rnorm(100, 3, 3)) head(data) # Head of example data
As you can see based on Table 1, our example data is a data frame consisting of 100 rows and three columns.
Example 1: Change Axis Labels of Boxplot Using Base R
In this section, I’ll explain how to adjust the x-axis tick labels in a Base R boxplot.
Let’s first create a boxplot with default x-axis labels:
boxplot(data) # Boxplot in Base R
The output of the previous syntax is shown in Figure 1 – A boxplot with the x-axis label names x1, x2, and x3.
We can rename these axis labels using the names argument within the boxplot function:
boxplot(data, # Change labels of boxplot names = c("Name_A", "Name_B", "Name_C"))
In Figure 2 you can see that we have plotted a Base R box-and-whisker graph with the axis names Name_A, Name_B, and Name_C.
Example 2: Change Axis Labels of Boxplot Using ggplot2 Package
It is also possible to modify the axis labels of a ggplot2 boxplot.
As a first step, we have to reshape our input data frame from wide to long format using the reshape2 package.
First, we need to install and load the reshape2 package:
install.packages("reshape2") # Install reshape2 package library("reshape2") # Load reshape2 package
Next, we can apply the melt function to transform our data frame:
data_long <- melt(data) # Reshape data head(data_long) # Head of reshaped data
In Table 2 you can see that we have created a data frame in long format.
As next step, we need to install and load the ggplot2 package:
install.packages("ggplot2") # Install ggplot2 package library("ggplot2") # Load ggplot2
Let’s draw a ggplot2 boxplot with default axis specifications:
ggplot(data_long, aes(variable, value)) + # Boxplot in ggplot2 geom_boxplot()
As shown in Figure 3, we have managed to create a ggplot2 boxplot using the previously shown R code.
The simplest solution for changing the x-axis labels is that we change the label names in our long data frame. Have a look at the R code below:
data_long_labels <- data_long # Duplicate data levels(data_long_labels$variable) <- c("Name_A", # Relevel factor labels "Name_B", "Name_C")
After executing the previous R code, our variable names were changed to Name_A, Name_B, and Name_C.
Next, we can use this updated data frame to create another boxplot with the ggplot2 package:
ggplot(data_long_labels, aes(variable, value)) + # Boxplot with updated labels geom_boxplot()
Figure 4 illustrates the output of the previous R programming syntax: A ggplot2 boxplot with renamed axis tick labels.
Video & Further Resources
I have recently published a video on my YouTube channel, which illustrates the R codes of this article. You can find the video below.
Furthermore, you might want to read the other articles of my website. You can find a selection of related tutorials below.
- Change Spacing of Axis Tick Marks in Base R Plot
- Change Font Size of ggplot2 Facet Grid Labels
- Rotate ggplot2 Axis Labels in R
- pretty Function in R
- Change Colors of Axis Labels & Values of Base R Plot
- Drawing Plots in R
- R Programming Tutorials
In this R tutorial you have learned how to modify boxplot axis labels. If you have further comments and/or questions, don’t hesitate to let me know in the comments section below.