[R] How to set an argument such that a function treats it as missing?

[Marius Hofert]

Ahh, thank you very much, precisely what I was looking for :-)))

Cheers,

Marius

On 2010-11-13, at 12:41 , Duncan Murdoch wrote:

> Marius Hofert wrote:
>> Dear expeRts,
>> I would like to call a function f from a function g with or without an argument. I use missing() to check if the argument is given. If it is not given, can I set it to anything such that the following function call (to f) behaves as if the argument
>> isn't given? It's probably best described by a minimal example (see below).
>> The reason why I want to do this is, that I do not have to distinguish between the
>> cases when the argument is given or not. By setting it to something (what?) in the
>> latter case, I can use the same code in the subsequent part of the function.
>> Cheers,
>> Marius
>> f <- function(x) if(missing(x)) print("f: missing x") else print(x)
>> g <- function(x){
>> 	if(missing(x)){
>> 		print("g: missing x")
>> 		x <- NULL # I try to set it to something here such that...
> 
> Just leave out the line above, and you'll get both messages printed:
> 
> > g()
> [1] "g: missing x"
> [1] "f: missing x"
> 
> Duncan Murdoch
> 
>> 	}
>> 	f(x) # ... this call to f behaves like f() } g() # should print "f: missing x" (is this possible?)
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>> and provide commented, minimal, self-contained, reproducible code.
>