Manipulating the “trellis” Object

The Trellis paradigm is different from traditional R graphics in an important respect: high-level “plotting” functions in lattice produce objects rather than any actual graphics output. As with other objects in R, these objects can be assigned to variables, stored on disk in serialized form to be recovered in a later session, and otherwise manipulated in various ways. They can also be plotted, which is all we want to do in the vast majority of cases. Throughout this book, we have largely focused on this last task. In this chapter, we take a closer look at the implications of the object-based design and how one might take advantage of it.