How To Center Plot Title In Ggplot2 With R - The Research Scientist Pod

The easiest way to center a title using ggplot2 is to modify the plot.title component of the theme using element_text(hjust=0.5). For example,

library(ggplot2) ggplot(data=mtcars, aes(x=mpg, y=wt)) + geom_point() + ggtitle("Automobile Weight vs Miles per Gallon") + theme(plot.title=element_text(hjust=0.5))

This tutorial will go through how to adjust the plot title using ggplot2 with code examples.

Table of contents

• Example
  • Center Aligned using hjust
  • Center Aligned using hjust and vjust
  • Right Aligned using hjust and vjust
• Summary

Example

Consider the following scatterplot of two variables from the mtcars dataset miles per gallon (mpg) and weight (wt).

library(ggplot2) # Create scatterplot using ggplot2 ggplot(data=mtcars, aes(x=mpg, y=wt)) + geom_point() + ggtitle("Automobile Weight vs Miles per Gallon")

By default, plot titles in ggplot2 are left-aligned.

Center Aligned using hjust

We can adjust the plot theme using plot.title and element_text. The function element_text specifies the display of the text component of the plot.

The hjust argument for element_text shifts the plot title text horizontally. If we set hjust to 0.5, we centre the title. Let’s look at the revised code:

library(ggplot2) ggplot(data=mtcars, aes(x=mpg, y=wt)) + geom_point() + ggtitle("Automobile Weight vs Miles per Gallon") + theme(plot.title=element_text(hjust=0.5))

We can see that the title is now centre-algined.

Center Aligned using hjust and vjust

We can shift the title horizontally and vertically using the hjust and vjust arguments. If we set vjust to a negative value the title moves down the plot, if we set it to a positive value the title moves up the plot. Let’s look at the revised code:

library(ggplot2) ggplot(data=mtcars, aes(x=mpg, y=wt)) + geom_point() + ggtitle("Automobile Weight vs Miles per Gallon") + theme(plot.title=element_text(hjust=0.5, vjust=-7))

We can see that the title has moved down and is inside the plot.

Right Aligned using hjust and vjust

We can set right-align the title by setting hjust to 1. Let’s look at the revised code:

ggplot(data=mtcars, aes(x=mpg, y=wt)) + geom_point() + ggtitle("Automobile Weight vs Miles per Gallon") + theme(plot.title=element_text(hjust=1, vjust=-7))

We can see that the title is right-aligned and shifted down inside the plot.

Summary

Congratulations on reading to the end of this tutorial!

For further reading on R, go to the articles:

• How to Transpose a Data Frame in R
• How to Apply a Function to Every Row of a Table in R using dplyr
• How to Remove Legend in ggplot2
• How to Solve R Error: ggplot2 doesn’t know how to deal with data of class uneval 

Go to the online courses page on R to learn more about coding in R for data science and machine learning.

Have fun and happy researching!

Suf

Senior Advisor, Data Science | [email protected] | + postsBio

Suf is a senior advisor in data science with deep expertise in Natural Language Processing, Complex Networks, and Anomaly Detection. Formerly a postdoctoral research fellow, he applied advanced physics techniques to tackle real-world, data-heavy industry challenges. Before that, he was a particle physicist at the ATLAS Experiment of the Large Hadron Collider. Now, he’s focused on bringing more fun and curiosity to the world of science and research online.

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