Writing Your Own Functions in R

Interactive beginner R tutorial on writing functions: function(){}, arguments, default values, return(), and applying a function across values. Run real R in your browser.

The moment you copy-paste the same code twice, it’s time to write a function. Everything below is a live R console — edit the code and press Run Code.

Watch: writing your own functions

Defining a function, giving arguments default values, returning a result, and applying it across many values.

Download the R script  ·  ▶ Practice in the playground — or edit and run each snippet below.

Your first function

function(args) { body }. Because R is vectorized, it works on one value or many for free:

Default argument values

Give an argument a default and the caller only supplies what they want to change:

Several steps, one result

Do the work, then hand back a value with return():

Functions + apply = power

Run your function across a whole set of inputs with the apply family:

Your turn

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Next: Installing & loading packages → — extending R beyond base.