*When R creates copies, and how it affects memory usage and code performance*Everything you could ever want to know about functions*The differences between calling and exiting handlers*How to employ functional programming to solve modular tasks*The motivation, mechanics, usage, and limitations of R's highly pragmatic S3 OO system*The R6 OO system, which is more like OO programming in other languages*The rules that R uses to parse and evaluate expressions*How to use metaprogramming to generate HTML or LaTeX with elegant R code*How to identify and resolve performance bottlenecks