Question

When reading scientific papers I often come across plots where points are jittered without overlaping each other. I suspect many of them are drawn with a program called GraphPad Prism, but surely there must be a way to do the same in R. Although it is not perfect (as with the red points below) I think it looks much better than random jittering.

If anybody knows how to do this, preferably using some basic function, I’d be very happy to know.

Answer 1

Here is a ggplot2 solution using geom_dotplot():

library(ggplot2)
set.seed(1234)

dat = data.frame(y=c(rpois(20, 4), rpois(20, 1), runif(20, 0, 20)), 
                category=rep(c("group_1", "group_2", "group_3"), c(20, 20, 20)))

dotplot_1 = ggplot(dat, aes(x=category, y=y)) + 
            geom_dotplot(aes(fill=category), binaxis="y", 
                         stackdir="center", binwidth=0.8) +
            stat_summary(fun.y=median, fun.ymin=median, fun.ymax=median, 
                         geom="crossbar", width=0.7)

ggsave("dotplot_1.png", dotplot_1, width=6, height=4)