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 the 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
Data and R Code Files
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 lesson by finishing our demonstration on package creation.