R in a Nutshell, 2nd Edition

An Overview of the Lattice Package

Lattice graphics consist of one or more rectangular drawing areas called panels. The data assigned to each panel is referred to as a packet. Lattice functions work by calling one or more panel functions, which actually plot the packets within panels. To change the appearance of a plot, you can specify arguments to the plotting function or change the panel function.

How Lattice Works

Here is what typically happens in a lattice session:

1. The end user calls a high-level lattice plotting function.

2. The lattice function examines the calling arguments and default parameters, assembles a lattice object, and returns the object. (Note that the class of the object is actually “trellis.” This means that many of the methods that act on an object, like print or plot, are named plot.trellis or print.trellis.)

3. The user calls print.lattice or plot.lattice with the lattice object as an argument. (This typically happens automatically on the R console.)

4. The function plot.lattice sets up the matrix of panels, assigns packets to different panels (specified by the argument packet.panel) and then calls the panel function specified in the lattice object to draw the individual panels.

Lattice graphics are extremely modular; they share many high-level functions (like plot.lattice) and low-level functions (like panel.axis, which draws axes). This means that they share many common arguments. It also means that you can customize the appearance of lattice graphics by creating substitute ...