I'd like to know if it is possible to change some default parameters of ggplot2 graphics, like font size for instance, for a whole R session. The idea is to avoid setting them for each plot.
To change the default font size in ggplot2, you can use the theme_set() function as follows:
theme_set(theme_gray(base_size = 15))
ggplot(mpg, aes(cty, hwy)) + geom_point()