Love this way how when combining #ggplot2 in #R with #gridExtra you can easily (very easy!!) add these density plots (thanks +Aylwyn Scally for pointing that out) on the top and side of your plot. Just pure awesome 🙂

For R code look at +Michael Kuhn blog:
http://blog.mckuhn.de/2013/04/2d-plot-with-histograms-for-each.html