The previous chapter introduced some basic features of plotting in R. This section will introduce the ggplot2 library. ggplot2 is based on concepts from Leland Wilkinson's The Grammar of Graphics, a classic in the data visualization field. The goal of this book was to provide an underlying theory of graphical data display. The framework provided aims to provide a unified viewpoint in which various tools (scatter plots, bar charts, pie charts, and so on) can all be viewed as special cases of a more general concept of graphical data presentation.
For more information on
ggplot2, see the home page for the project at http://ggplot2.org/ and the documentation at http://docs.ggplot2.org/current/index.html.