11.4 Changing the Appearance of Facet Labels and Headers
11.4.1 Problem
You want to change the appearance of facet labels and headers.
11.4.2 Solution
With the theming system, set strip.text to control the text appearance and strip.background to control the background appearance (Figure 11.6):
library(gcookbook) # Load gcookbook for the cabbage_exp data set
ggplot(cabbage_exp, aes(x = Cultivar, y = Weight)) +
geom_col() +
facet_grid(. ~ Date) +
theme(
strip.text = element_text(face = "bold", size = rel(1.5)),
strip.background = element_rect(fill = "lightblue", colour = "black", size = 1)
)
Figure 11.6: Customized appearance for facet labels
11.4.3 Discussion
Using rel(1.5) makes the label text 1.5 times the size of the base text size for the theme. Using size = 1 for the background makes the outline of the facets 1 mm thick.