The statistical language R has proven to be a popular choice among statisticians, researchers, and organizations for statistical analysis and graphs. This is partly due to the free nature of the program and the power of its programming capabilities. Other strengths include its exceptionally good support, its continual improvement (updates occur almost monthly at times), and its very active user community. R is a model example of the benefits of free and open-source software, and a wealth of contributed documentation is freely available. In recent years, the R language has amassed a growing, and very strong, supporting literature, which consists of several introductory texts and companions to existing textbooks and which implements modern statistical methods, regression modeling strategies, and specialized types of models. R integrates ...