R graphs: Creating Tufte's horizontal bar lines

Question

How can we replicate Tufte\'s implicit horizontal lines in R?

For example, the following

Answer 1

In principle, this is straightforward - all you need to do is draw white horizontal lines in a new layer. You can use geom_hline to do this:

library(ggplot2)    
ggplot(msleep, aes(x=order)) + stat_bin() + theme_bw() +
  geom_hline(yintercept=seq(5, 20, 5), col="white")

As for your second question - I'd imagine this may be hard to incorporate in a theme, although it should be possible to create a custom geom that reads the y-scale breaks and plot the lines correspondingly.

(I'd love to be proved wrong.)