In the previous chapter, we discovered how to easily visualize our data using standard functions of R. You might remember that at some point, when discussing bar plots, we visualized the frequency of an attribute based on the case's membership a group. This required that we generated several plots, each displaying the data in one of the groups. Dealing with this kind of issue more easily is mostly what trellis graphics are about.
Trellis graphics allow the visualization of data based on group membership effortlessly. With features such as multipanel conditioning (Becker & Cleveland, 1996, p. 6), understanding the structure of your data becomes a seamless visualizing experience.
Multipanel conditioning means that data is displayed on multiple panels which are defined as a function of group membership. It is particularly interesting when membership to several characteristics are involved (for instance age group and gender). In these cases we are...