Or yet another way which is (I think) a bit closer to your requirement...
f <- function(x) {
if (missing(x)) cat("x is missing \n")
else cat("x was provided \n")
}
g <- function(x) {
if (missing(x))
fcall <- call("f")
else
fcall <- call("f", x)
eval(fcall)
}
On 13 November 2010 20:24, Michael Bedward <michael.bedw...@gmail.com> wrote:
> Hello Marius,
>
> NULL is not the same as missing. You could something like this in
> various ways. Here are a couple...
>
> g <- function(x) {
> if (missing(x)) {
> f()
> } else {
> f(x)
> }
> }
>
> or change f to detect null args
>
> g <- function(x) {
> if (missing(x)) {
> x <- NULL
> }
>
> f(x)
> }
>
> f <- function(x) {
> if (missing(x) | is.null(x)) {
> // do something
> }
> }
>
>
> Michael
>
>
> On 13 November 2010 19:14, Marius Hofert <m_hof...@web.de> 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...
>> }
>> f(x) # ... this call to f behaves like f()
>> }
>>
>> g() # should print "f: missing x" (is this possible?)
>> ______________________________________________
>> R-help@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
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