• Functions in R are objects that allow you to package a sequence of statements to perform a specific task, improving code reusability and organization.

• They can take inputs, perform an operation, and return an output.

function_name <- function(parameters) {
  # Block of code
  return(result)
}

• A function is defined using the function keyword.

• The inputs are specified within the parentheses. They represent the inputs the function can accept.

• The body of the function is enclosed in {}.

• The return() statement is used to return the result of the function.

• If return() is not explicitly called, the last line is returned automatically.

greet <- function(name) {
  paste("Hello,", name, "!")
}

• The greet function takes a single argument, name.

• It returns a string that greets the user by name.

greet <- function(name) {
  paste("Hello,", name, "!")
}

message <- greet("Alice")
print(message)  # Outputs: Hello, Alice !

## [1] "Hello, Alice !"

• After defining a function, call it by using its name followed by parentheses () enclosing any arguments.

• Parameters are the placeholders used in the function’s definition.

• Arguments are the actual values passed to the function when it is called.

Functions in R can have default parameter values, making some arguments optional.

greet <- function(name="World") {
  paste("Hello,", name, "!")
}

Pass arguments to a function with or without specifying their names.

describe_pet <- function(animal_type, pet_name) {
  cat("I have a", animal_type, "named", pet_name, ".\n")
}

describe_pet(pet_name="Whiskers", animal_type="cat")

## I have a cat named Whiskers .

How do you define a function in R that takes no arguments and prints “Hello, World!”?

1. function() {print("Hello, World!")}
2. myFunc <- print("Hello, World!")
3. myFunc <- function() {print("Hello, World!")}
4. function myFunc() {return("Hello, World!")}

Answer 1

Given a function addNumbers that takes two arguments, x and y, and returns their sum, which of the following calls is correct?

1. addNumbers(x, y)
2. addNumbers <- (x + y)
3. result <- addNumbers(2, 3)
4. result = addNumbers(x: 2, y: 3)

Answer 2

What is the output of the following code?

add <- function(x, y) {
  return(x + y)
}

print(add(5, 3))

## [1] 8

1. 8
2. 53
3. “x + y”
4. Error

How do you define a function with one compulsory parameter name and one optional parameter age with a default value of 30 in R?

1. person <- function(name, age=30) {# do stuff}
2. person <- function(name=30, age) {# do stuff}
3. person <- function(name, age) {# do stuff}
4. person <- function(name, optional age=30) {# do stuff}}

Given the describe_pet function below, which of the following calls to describe_pet is correct in R?

describe_pet <- function(animal_type, pet_name) {
  cat("I have a", animal_type, "named", pet_name, ".\n")
}

1. describe_pet("dog", "Rover")
2. describe_pet(pet_name="Daisy", animal_type="cat")
3. describe_pet(animal_type="hamster")
4. describe_pet("Daisy", animal_type="dog")