Re: [R] Optional variables in function?

From: Joerg van den Hoff <j.van_den_hoff_at_fz-rossendorf.de>
Date: Mon 03 Jul 2006 - 23:36:18 EST

jim holtman wrote:
> ?missing
>
> On 7/2/06, Jonathan Greenberg <jgreenberg@arc.nasa.gov> wrote:
>> I'm a bit new to writing R functions and I was wondering what the "best
>> practice" for having optional variables in a function is, and how to test
>> for optional and non-optional variables? e.g. if I have the following
>> function:
>>
>> helpme <- function(a,b,c) {
>>
>>
>> }
>>
>> In this example, I want c to be an optional variable, but a and b to be
>> required. How do I:
>> 1) test to see if the user has inputted c
>> 2) break out of the function of the user has NOT inputted a or b.

if(missing(c))

    stop("need c")

or

if(missing(c))

    return()

depending on your problem it might be better to provide sensible default values for a,b,c in the function definition

helpme<-function(a=A, b=B, c=C) {...}

instead of enforcing that every argument is specified?

joerg

>>
>> Thanks!
>>
>> --j
>>
>> --
>>
>> Jonathan A. Greenberg, PhD
>> NRC Research Associate
>> NASA Ames Research Center
>> MS 242-4
>> Moffett Field, CA 94035-1000
>> Phone: 415-794-5043
>> AIM: jgrn3007
>> MSN: jgrn3007@hotmail.com
>>
>> ______________________________________________
>> R-help@stat.math.ethz.ch mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide!
>> http://www.R-project.org/posting-guide.html
>>
>
>
>



R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Jul 04 00:50:48 2006

Archive maintained by Robert King, hosted by the discipline of statistics at the University of Newcastle, Australia.
Archive generated by hypermail 2.1.8, at Tue 04 Jul 2006 - 02:14:53 EST.

Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-help. Please read the posting guide before posting to the list.