Functions
Part III covers the basics of functions. Functions are a class of objects that are essentially computer programs. There are tens of thousands of prepackaged functions in R. The user can also develop functions. Chapter 6 describes packaged functions; Chapter 7 shows you how to create new functions; and Chapter 8 explains how to use functions.
When you install R, thirty packages are installed at the same time by default. You can install other packages later. On your computer, packaged functions are stored in packages, which are stored in libraries.
Chapter 6 describes the libraries, lists the packages that are loaded by default when R opens, discusses the primitive functions, gives advice on using help pages, and provides some useful functions related to packages.
Chapter 7 describes the structure of functions. It presents several methods that can be used to create a function and import the function into the R workspace, including the following: using an editor internal to R, inputting the function directly at the console, using an editor external to R with dget(), and cutting and pasting into R.
Chapter 8 discusses how to call a function, how to use arguments, and what to expect for output.