Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

Functions allows you to divide your large lines of code into smaller ones. Usually the division happens logically such that each function performs a specific task and is up to developer.

R provides a large number of in-built functions (refer here) and users also can create their own functions.

How to define a Function

function_name <- function(arg1, arg2, ...) {
  #code 
}

How to call a Function

function_name(arguments)

Examples

1. Function with no arguments

greetings <- function() {
  print("I'm in function")
}

greetings()

Check Result here

2. Function with arguments

sum <- function(x, y) {
  cat("Sum:", x+y)
}

sum(10, 20)

Check Result here