R Graphics Cookbook

Chapter 9. Controlling the Overall Appearance of Graphs

In this chapter I’ll discuss how to control the overall appearance of graphics made by ggplot2. The grammar of graphics that underlies ggplot2 is concerned with how data is processed and displayed—it’s not concerned with things like fonts, background colors, and so on. When it comes to presenting your data, there’s a good chance that you’ll want to tune the appearance of these things. ggplot2’s theming system provides control over the appearance of non-data elements. I touched on the theme system in the previous chapter, and here I’ll explain a bit more about how it works.

Setting the Title of a Graph

Problem

You want to set the title of a graph.

Solution

Set title with ggtitle(), as shown in Figure 9-1:

library(gcookbook) # For the data set

p <- ggplot(heightweight, aes(x=ageYear, y=heightIn)) + geom_point()

p + ggtitle("Age and Height of Schoolchildren")

# Use \n for a newline
p + ggtitle("Age and Height\nof Schoolchildren")

Figure 9-1. Left: scatter plot with a title added; right: with a /n for a newline

Discussion

ggtitle() is equivalent to using labs(title = "Title text").

If you want to move the title inside the plotting area, you can use one of two methods, both of which are a little bit of a hack (Figure 9-2). The first method is to use ggtitle() with a negative vjust value. The drawback of this method is that it still reserves ...