Lesson 20: Writing Functions and Packages

Overview

In this chapter of Essential R we'll take a look at writing functions, debugging them, and also at creation of packages.

Objectives

Upon completion of this lesson, you should be able to:

Write simple functions with default arguments
Control how values are returned by your function
Debug a function
Recognize and prevent some common errors in user-created functions
Create a simple package

R

The R code file and data files for this lesson can be found on the Essential R - Notes on learning R page.

20.1 - Creating a Function

Here we'll demonstrate the most basic creation of a function using the function function ().

20.2 - Specifying Default Values for Arguments

Now we'll consider how default values for arguments are specified. Also, we'll discuss how functions are evaluated (hint: not in user workspace).

20.3 - Returning Values

In this video we'll consider how to return single or multiple values from a function.

20.4 - Functions That Change Objects Are Risky

In this video I will try to convince you that it is probably not a good idea to write functions that change objects in your environment, but then I will show you how to do it anyway, and duscuss under what (rare) circumstances it might make sense to do this.

20.5 - Debugging Errors and Checking Inputs

Here we will discuss debugging errors and checking inputs when a function is called.

20.6 - Sneaky Errors - NA Values

We'll conclude our discussion of writing functions by considering how NA values may affect functions.

20.7 - Creating a Package Part I

Now we'll consider why you might want to create a package, and how you would go about doing so.

20.8 - Creating a Package Part II

We'll conclude this Chapter by finishing our demonstration on package creation.

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