Functions in R

Introduction

Functions are reusable blocks of code that perform specific tasks. They are essential for writing modular and maintainable R code.

Creating Functions

# Simple function
greet <- function() {
  print("Hello, World!")
}
greet()

# Function with parameter
greet_name <- function(name) {
  paste("Hello,", name)
}
greet_name("Alice")

# Function with default parameter
greet_name <- function(name = "World") {
  paste("Hello,", name)
}
greet_name()

Return Values

# Using return()
add <- function(a, b) {
  return(a + b)
}

# Last expression is returned
add <- function(a, b) {
  a + b  # Returns automatically
}

Multiple Parameters

# Multiple parameters
calculate <- function(a, b, operation = "add") {
  switch(operation,
    "add" = a + b,
    "sub" = a - b,
    "mul" = a * b,
    "div" = a / b
  )
}
calculate(10, 5, "add")

Variable Scope

# Global vs local variables
x <- 10

test_scope <- function() {
  y <- 5       # Local variable
  print(x)     # Access global
  print(y)
  x <<- 20     # Modify global
}

test_scope()
print(x)

Anonymous Functions

# Anonymous function
(function(x) x^2)(5)

# Apply anonymous function
sapply(1:5, function(x) x^2)

Summary

Functions are fundamental to R programming. Create well-documented functions for reusable code.