Update 14/02/2021: The book's official website network-theory.co.uk is no longer online. We switched the download link to a local copy.
Book excerpts:

This manual is the second volume of the complete reference manual for the base package of GNU R, a free software environment for statistical computing and graphics. The commands for graphics, mathematics, distributions and random numbers, models, time-series and datasets are described in this volume.

The companion first volume 'The R Reference Manual - Base Package - Volume 1' (ISBN 0-9546120-0-0) contains documentation for the core programming commands and functions. Together the first and second volumes document the complete base package of R (version 1.8.1).

All the reference manuals are written by the developers of R, and represent the definitive guide to the software. The manuals explain the use of each command in detail, with references, implementation notes and examples. Every volume includes a comprehensive index of entries listed by keyword and topic.

NOTE: You need both volumes (1 & 2) for the complete documentation. The individual volumes are not intended to be used on their own.