In R you can use '...' for the function to receive an indeterminate number of arguments.
How do I know which arguments were used in the function?
Example, if I wanted to print the arguments used.
imprimeArgumentos <- function(...) {
args <- #pega os argumentos contidos em ´...´
print(args)
}
The function should work as follows.
imprimeArgumentos(x=3, z=NULL, y=3)
$x
[1] 3
$z
NULL
$y
[1] 3
A simple way to capture the arguments is to put them in a list:
imprimeArgumentos <- function(...) {
args <- list(...)
print(args)
}
imprimeArgumentos(x=3, z=NULL, y=3)
#> $x
#> [1] 3
#>
#> $z
#> NULL
#>
#> $y
#> [1] 3
If you want to work with lazy evaluation, you can use substitute and only evaluate arguments when appropriate:
imprimeArgumentos <- function(...) {
# vai te retornar uma expressão da lista e não a lista em si
args <- substitute(list(...))
print(args)
}
imprimeArgumentos(x=3, z, y=3)
#> list(x = 3, z, y = 3)
Note that in this last example, z does not exist, but function does not give an error because we have not yet evaluated the contents of the list.