ABSTRACT
In this chapter you will learn how to expand the range of features available. Use of packages is equivalent to importing ready defined “words”, while defining new functions, operators and classes is similar to defining new “words” such verbs and nouns. In the first part of the chapter you will learn how to define new functions, operators and classes. In the second part you will learn how to use existing packages such as those available for download from CRAN, the comprehensive R archive network, and how they expand the functionality of R.
