There are different kinds of tools for data visualization and ggplot2 is always my favorite. It is powerful, elegant and easy to use except for one minor defect — difficulty of adding footnote. Unlike adding title, it’s no explicit statement available to add a footnote directly. Let’s use the following plot as example (according to the mpg data set included in ggplot2).
library(ggplot2) toyota <- mpg[which(mpg$manufacturer == 'toyota'), ] p <- ggplot(toyota, aes(displ, hwy)) + facet_wrap(~ class, ncol = 2) + geom_point(aes(size=cyl)) print(p)
As you can see, I create a 4-panel scatter plot using displ as x-axis and hwy as y-axis. Let’s see how we can add the footnote to the plot.