... and you could also use missing() (?missing for details) if you
wanted to give the user more verbose instructions, e.g.
f1 <- function(type, ...) {
if(missing(type)){
cat("You must enter a 'type' argument that is one of etc....\n")
return(invisible())
}
match.arg(type, c("A", "B", "C"))
}
Bert Gunter
"Data is not information. Information is not knowledge. And knowledge
is certainly not wisdom."
-- Clifford Stoll
On Wed, Aug 19, 2015 at 9:19 AM, William Dunlap <wdun...@tibco.com> wrote:
> If you want to force the user to enter the 'type' argument,
> move the vector of choices out of the argument list
> and into the call to match.arg():
>
> f1 <- function(type, ...) {
> match.arg(type, c("A", "B", "C"))
> }
> f1()
> #Error in match.arg(type, c("A", "B", "C")) :
> # argument "type" is missing, with no default
> f1("X")
> #Error in match.arg(type, c("A", "B", "C")) :
> # 'arg' should be one of “A”, “B”, “C”
> f1("B")
> #[1] "B"
>
>
> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com
>
> On Tue, Aug 18, 2015 at 5:42 PM, Youyi Fong <yf...@fhcrc.org> wrote:
>
>> Hello, I have a function that looks like
>>
>> f=function( type=c("dummy,"A","B,"C"), ... ) {
>> type<-match.arg(type)
>> if (type=="dummy") stop("Please choose a type that is not dummy.")
>> ...
>> }
>>
>> I put a "dummy" in the list of choices as a mechanism to prevent users
>> from not specifying a value for "type" when calling the function. My
>> question is whether there is a better way to achieve it that does not
>> need "dummy".
>>
>> Thanks,
>> Youyi
>>
>> ______________________________________________
>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> 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.
>>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.
______________________________________________
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
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.
