This is a tiny post, but if I lumped it as an aside into a longer post I might never find it again. If you’re trying to keep up with Hadley Wickham you might need to update R from time to time. The installr package is there to help you keep up with the Wickhams. To update R, just follow the following steps:

install.packages("installr");
library(installr);
updateR();

For further infromation, check out this r-statistics post on the topic.