Warning! This document is not for those who are fairly new to R. I don’t want you to get scared away!
Any software system of any type is going to have a few idiosyncracies. But the R programming language has an abundance of them. These aren’t bugs, just unexpected behaviors. Understand the counter-intuitive behavior of these idiosycracies and you will be a better R programmer. Patrick Burns has an extensive list of the odd things that R will do from time to time. This is part of a series of tutorials written by this author.
Patrick Burns. The R Inferno.