Function

Function is one of the most important concepts in R programming. You use functions to do something with the input. For example, print() is a function, but we are occasionally interested in creating a more complicated function to manipulate the data.

The basic structure of a function is:

function_name <- function(arg_1, arg_2, ...) {
   Function body 
}

Here, you put the arugments that you would like to use in the function inside the parenthesis, and write the things that you would like the function to do at the Function body part.

We will show you some examples of functions below:

Example 1: Adding two numbers

add_number <- function(a, b){
  result <- a + b
  result
}

Here, I put a and b inside the parenthesis, because I would like to use them inside the function.

add_number(2, 4)

## [1] 6

In this code, add_number is the name of the function, and (2, 4) means that I specify a=2 and b=4.

Example 2: Calculate tip

We assume that the tip percentage is 20%. We will create a function that determines the tip price from the total.

tip <- function(price){
  tip <- price * 0.2
  tip
}

tip(200)

## [1] 40

Functions can be used to make the codes short and easier to understand. You can also use functions to do tedious things in programming.

We will be using functions in future labs to do things more simply.