Editing R (programming language) (section)

=== Structure of a function ===
R is able to create [[Function (computer programming)|functions]] to add new functionality for reuse.<ref>{{cite web|url=http://www.statmethods.net/management/userfunctions.html|title=Quick-R: User-Defined Functions|first=Robert|last=Kabacoff|year=2012|access-date=2018-09-28|website=statmethods.net}}</ref> [[Object (computer science)|Objects]] created within the body of the function (which are enclosed by curly brackets) remain [[Local variable|only accessible]] from within the function, and any [[data type]] may be returned. In R, almost all functions and all [[user-defined function]]s are [[closure (computer programming)|closures]].<ref>{{cite web|url=http://adv-r.had.co.nz/Functional-programming.html#closures|title=Advanced R - Functional programming - Closures|website=adv-r.had.co.nz|first=Hadley|last=Wickham}}</ref>

Example of creating a function to perform some arithmetic calculation:
<syntaxhighlight lang="r"># The input parameters are x and y.
# The function, being named f, returns a linear combination of x and y.
f <- function(x, y) {
  z <- 3 * x + 4 * y

  # An explicit return() statement is optional, could be replaced with simply `z`.
  return(z)
}

# Alternatively, the last statement executed is implicitly returned.
f <- function(x, y) 3 * x + 4 * y</syntaxhighlight>

Usage output:
<syntaxhighlight lang="rout">
> f(1, 2) #  3 * 1 + 4 * 2 = 3 + 8
[1] 11

> f(c(1, 2, 3), c(5, 3, 4)) # Element-wise calculation
[1] 23 18 25

> f(1:3, 4) # Equivalent to f(c(1, 2, 3), c(4, 4, 4))
[1] 19 22 25
</syntaxhighlight>

It is possible to define functions to be used as [[Infix notation|infix operators]] with the special syntax <code>`%name%`</code> where "name" is the function variable name:
<syntaxhighlight lang="rout">
> `%sumx2y2%` <- function(e1, e2) {e1 ^ 2 + e2 ^ 2}
> 1:3 %sumx2y2% -(1:3)
[1]  2  8 18 
</syntaxhighlight>

Since version 4.1.0 functions can be written in a short notation, which is useful for passing anonymous functions to higher-order functions:<ref>{{cite web|url=https://cran.r-project.org/doc/manuals/r-release/NEWS.html#:~:text=R%20now%20provides%20a%20shorthand%20notation%20for%20creating%20functions|title=NEWS|website=r-project.org}}</ref> 
<syntaxhighlight lang="rout">
> sapply(1:5, \(i) i^2)    # here \(i) is the same as function(i) 
[1]  1  4  9 16 25
</syntaxhighlight>