2.4 Functions in R
Related Reading: IDS 2.2
R has a large number of helpful, built-in functions. Let’s start with a pretty representative example: computing logarithms. This can be done using the R function log.
You can tell this is a function because of the parentheses. The 5 inside of the parentheses is called the argument of the function. As practice, try computing the \(\log\) of 7.
The default base in R is \(e \approx 2.718\), so that log(5) actually computes what you might be more used to calling the “natural logarithm”. You can change the default value of the base by adding an extra argument to the function.
In order to learn about what arguments are available (and what they mean), you can access the help files for a particular function by running either
and, of course, substituting the name of whatever function you want to learn about in place of log.
In RStudio, it can also be helpful to press Tab and RStudio will provide possible completions to the function you are typing as well as what arguments can be provided to that function.
Practice: R has a function for computing absolute value (you’ll have to find the name of it on your own). Try computing the absolute value of \(5\) and \(-5\). Try creating a variable called negative_three that is equal to \(-3\); then, try to compute the absolute value of negative_three.
Side Comment: As a reminder, the logarithm of some number, let’s call it \(b\), is is the value of \(a\) that solves \(\textrm{base}^a = b\).