Anonymous functions in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an anonymous function in R?

An anonymous function in R is a function without a name. It is often used for short tasks and passed directly as an argument to other functions.

beginner

How do you define an anonymous function in R?

You define it using the syntax: function(args) expression. For example, function(x) x + 1 is an anonymous function that adds 1 to its input.

intermediate

Why use anonymous functions instead of named functions?

Anonymous functions are useful for quick, simple tasks where defining a full named function is unnecessary. They keep code concise and are often used inside functions like lapply() or sapply().

beginner

Example: What does this code do? <br>lapply(1:3, function(x) x * 2)

It applies the anonymous function function(x) x * 2 to each element of the list 1, 2, 3. The result is a list with elements 2, 4, and 6.

intermediate

Can anonymous functions have multiple arguments in R?

Yes, anonymous functions can have multiple arguments. For example, function(x, y) x + y adds two inputs without needing a name.

What is the correct way to write an anonymous function that squares a number in R?

A function(x) x^2

B square <- function(x) x^2

C def square(x): x^2

D func(x) {x * x}

Anonymous functions in R use the syntax function(args) expression. Option A correctly defines an anonymous function that squares x.

Which function commonly uses anonymous functions as arguments in R?

A read.csv()

B print()

C lapply()

D setwd()

lapply() applies a function to each element of a list and often uses anonymous functions for quick operations.

What is the main benefit of using anonymous functions?

A They allow quick, inline function definitions without naming.

B They run faster than named functions.

C They can only be used once in a program.

D They automatically save results to a file.

Anonymous functions let you write small functions quickly without creating a separate named function.

Can anonymous functions in R have no arguments?

A No, they must have at least one argument.

B Yes, you can write function() expression.

C Only if you assign them to a variable.

D Only inside loops.

Anonymous functions can have zero or more arguments. For example, function() 42 returns 42.

What does this code return? <br>sapply(1:3, function(x) x + 5)

A A single number 8

B A list: 6, 7, 8

C An error

D A vector: 6, 7, 8

sapply() returns a simplified vector applying the anonymous function to each element, adding 5 to 1, 2, and 3.

Explain what an anonymous function is in R and give a simple example.

Think about functions without names used directly inside other functions.

Describe a situation where using an anonymous function is better than a named function in R.

Consider when you want to do something simple just once.