R Basics: Functions

Functions

• The R function called function() tells R you are about to define a new function.
• Functions are objects, so must be assigned a variable name with the arrow operator.
• The general way to define functions is: (1) decide the function name, which will be an object, (2) type function() with your function's arguments in parentheses, (3) write all the operations inside brackets.
• Variables defined inside a function are not saved in the workspace.

Code: Functions Example

# example of defining a function to compute the average of a vector x
avg <- function(x){
  s <- sum(x)
  n <- length(x)
  s/n
}

# we see that the above function and the pre-built R mean() function are identical
x <- 1:100
identical(mean(x), avg(x))

# variables inside a function are not defined in the workspace
s <- 3
avg(1:10)
s

# the general form of a function
my_function <- function(VARIABLE_NAME){
  perform operations on VARIABLE_NAME and calculate VALUE
  VALUE
}

# functions can have multiple arguments as well as default values
avg <- function(x, arithmetic = TRUE){
  n <- length(x)
  ifelse(arithmetic, sum(x)/n, prod(x)^(1/n))
}