Functions are fundamental building blocks in R programming. Learn to create and use functions to write modular, reusable, and efficient R code.
R Functions Tutorial
1. Function Basics
Creating and using simple functions in R:
# Basic function structure
function_name <- function(arguments) {
# Function body
return(value)
}
# Example: Square a number
square <- function(x) {
return(x * x)
}
square(5) # Returns 25
# Function with default argument
greet <- function(name = "Guest") {
paste("Hello,", name)
}
greet() # Returns "Hello, Guest"
greet("Alice") # Returns "Hello, Alice"Function Basics Quiz
What keyword is used to return a value from a function?
2. Function Arguments
Different ways to handle function parameters:
# Positional arguments
power <- function(x, exponent) {
x^exponent
}
power(2, 3) # 8
# Named arguments
power(exponent = 3, x = 2) # 8
# Variable number of arguments
sum_all <- function(...) {
sum(...)
}
sum_all(1, 2, 3, 4) # 10
# Argument checking
safe_divide <- function(a, b) {
if (b == 0) stop("Cannot divide by zero")
a / b
}Arguments Quiz
How do you specify a default argument value?
3. Return Values
Understanding function outputs in R:
# Explicit return
add <- function(a, b) {
return(a + b)
}
# Implicit return (last expression)
multiply <- function(a, b) {
a * b
}
# Returning multiple values
stats <- function(x) {
list(mean = mean(x), sd = sd(x), length = length(x))
}
# Returning invisible values (for printing control)
quiet <- function(x) {
invisible(x)
}Return Values Quiz
What does R return if there's no explicit return statement?
4. Advanced Function Concepts
Powerful function techniques in R:
# Anonymous functions (lambdas)
sapply(1:5, function(x) x^2)
# Function factories
power_factory <- function(exponent) {
function(x) {
x^exponent
}
}
square <- power_factory(2)
cube <- power_factory(3)
# Recursive functions
factorial <- function(n) {
if (n <= 1) return(1)
n * factorial(n - 1)
}
# Closures
counter <- function() {
count <- 0
function() {
count <<- count + 1
count
}
}Advanced Functions Quiz
What is a function that creates other functions called?
5. Function Best Practices
Writing clean, maintainable functions:
# Good practices:
# 1. Single responsibility principle
calculate_stats <- function(x) {
c(mean = mean(x), median = median(x), sd = sd(x))
}
# 2. Meaningful names
calculate_bmi <- function(weight_kg, height_m) {
weight_kg / (height_m^2)
}
# 3. Input validation
validate_percentage <- function(x) {
stopifnot(is.numeric(x), x >= 0, x <= 100)
# Function continues...
}
# 4. Document your functions
#' Calculate body mass index
#'
#' @param weight_kg Weight in kilograms
#' @param height_m Height in meters
#' @return Numeric BMI value
calculate_bmi <- function(weight_kg, height_m) {
weight_kg / (height_m^2)
}Best Practices Quiz
What's the best approach for a function that does multiple unrelated tasks?
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