It is assumed that you will be working in the R environment, and the example code has been developed and tested for R version 3.0.1 and later. The R environment is a type of free software and is made available through the efforts and generosity of the R Foundation. It can be downloaded from http://www.r-project.org/. The material in the first half of the book assumes that you have access to R and can work from the interactive command line within the R environment. The material in the second half of the book assumes that you are familiar with programming and can write and save computer code. At a minimum, you should have access to a programming editor and should be familiar with directory structures and search paths.