How to change the default font size in ggplot2
Use theme_set()
theme_set(theme_gray(base_size = 18))
qplot(1:10, 1:10)
Use theme_set if you want to update for the remainder of your active session:
theme_set(theme_grey(base_size = 18))
If you only want to change one graph you can set the base_size in the theme:
qplot(1:10, 1:10) + theme_grey(base_size = 18)
ggplot(mtcars, aes(x = mpg, y = cyl)) +
geom_point() +
theme_grey(base_size = 18)