ggplot2 footnote

16
votes

What is the best way to add a footnote to the bottom of a plot created with ggplot2? I've tried using a combination of the logic noted here as well as the ggplot2 annotate function. 

p + annotate("text",label="Footnote",
  x=unit(1,"npc") - unit(2, "mm"),y=unit(2, "mm"),
  just=c("right", "bottom"),gp=gpar(cex= 0.7, col=grey(.5)))

but I am getting the error

Error in as.data.frame.default(x[[i]], optional = TRUE, stringsAsFactors = stringsAsFactors) : cannot coerce class c("unit.arithmetic", "unit") into a data.frame

2
rpdfggplot2
This works if you view the plot in R but it doesn't look like it works with the ggsave function. - user338714
Then open an appropriate graphics device instead of using ggsave(), e.g., pdf("filename.pdf", width=10, height=6); print(p); grid.text(...); dev.off() - rcs

2 Answers

21
votes

labs(caption = "my caption") adds a footnote:

ggplot(mtcars, aes(mpg, wt, colour = cyl)) + 
  geom_point() + 
  labs(caption = "(Pauloo, et al. 2017)")

enter image description here

12
votes

I would use something like that:

pdf("filename.pdf", width=10, height=6) # open an appropriate graphics device
print(p)
makeFootnote() # from webpage above (uses grid.text; ggplot2 is based on grid)
dev.off()