Extending lattice: using generics and methods to implement new visualization methods within the Trellis framework

摘要

The lattice add-on package implements Trellis graphics in R. One of the major recent changes to the package API has been to make all high level functions generic, with the traditional implementations available as the “formula” method. This allows for cleaner and more flexible implementations for certain uses that were permitted in the original S-PLUS version on a one-off basis. For example, dotplot could be used to display one-way tables, but the new approach naturally extends to multi-way tables as well. More importantly, it opens up the possibility of new Trellis displays specifically designed for previously unsupported classes. We present some examples of such extensions and describe a few issues generally relevant to the development of new Trellis-style visualizations using the lattice infrastructure.