RstatisTik/RstatisTikPortal/RcourSe/CourseOutline/FunctionsInR/ApplyR

Every function in R has three important characteristics:

a body (the code inside the function) - body()
arguments (the list of arguments which controls how you can call the function) - formals()
an environment (the “map” of the location of the function’s variables) - environment()

You can see all three parts if you type the name of the function without brackets. Exceptions are primitives. Primitive functions, like sum(), call C code directly with .Primitive() and contain no R code. Therefore their formals(), body(), and environment() are all NULL.

Functions

   1 > chisq.test
   2 function (x, y = NULL, correct = TRUE, p = rep(1/length(x), length(x)),
   3 DNAME <- deparse(substitute(x))
   4 if (is.data.frame(x))
   5 expected = E, residuals = (x - E)/sqrt(E), stdres = (x - ...
   6 
   7 > sum
   8 function (..., na.rm = FALSE)  .Primitive("sum")

Function Arguments

Arguments are matched

first by exact name (perfect matching)
then by prefix matching
and finally by position.

By default, R function arguments are lazy, they are only evaluated if they are actually used:

   1 > f <- function(x) {
   2 f <- function(x) {
   3 +   10
   4 + }
   5 > f(stop("This is an error!"))
   6 [1] 10
   7 >

Introduction

Functions

Function Arguments