Functions

Functions let you package up a piece of logic so you can reuse it without rewriting it. In R, you create functions with the function() keyword. They can take inputs (parameters) and send back a result. The beauty is that once you've written a function, you can call it from anywhere in your script.

Defining a Function

Use function followed by parentheses for parameters and curly braces for the body. R returns the last expression automatically — but you can also use return() to be explicit.

# Simple function — last expression is returned
square <- function(x) {
  x * x
}

square(5)

# Function with return() explicitly
greet <- function(name) {
  return(paste("Hello,", name))
}

greet("Alice")

Multiple Parameters

You can pass multiple arguments. R matches them by position or by name. Default values make parameters optional.

add <- function(a, b = 0) {
  a + b
}

add(3, 4)
add(3)  # uses default b = 0

Functions That Return Nothing

Sometimes you want a function to do something — like print a message — without returning a value. That's fine too. Invisible NULL is returned by default.

show_info <- function(name, age) {
  cat(name, "is", age, "years old.\n")
}

show_info("Bob", 28)