You can add
+ theme_classic() to your ggplot to see what it does. ggplot has several built-in "themes" that customize the overall look of the plot in various ways. The default theme is
theme_grey(). You can change this for all future plots by running, for example:
To see available themes in ggplot, see the help for any theme. For example, run
?theme_classic(). The help page that opens will list all of the available themes. The
ggthemes package has more, and you can of course create your own.
To tweak any theme, add a
theme() statement to a ggplot after setting the overall theme. For example:
ggplot(mtcars, aes(mpg, hp)) +
See here and here for web versions of theme help files.
Here are some examples of how ggplots look with various themes.