Dear Franklin
thank you for this.
Your suggestion works. But now I'm confused because I'm not sure how
the
setGeneric() call actually helps.
If I source:
setClass("brob",
representation = representation
(x="numeric",positive="logical"),
prototype = list(x=numeric(),positive=logical())
)
max.brob <- function(..., na.rm=FALSE){stop("not YET implemented")}
---ie no call to setGeneric()--- then in an R session I can do the
following:
R> x <- new("brob",x=6,positive=T)
R> max(x)
Error in max.brob(..., na.rm = na.rm) : not YET implemented
So max(x) calls max.brob() as intended. Why would a call to
setGeneric()
be desirable here? What do I gain from it?
thanks again
Robin
On 4 Sep 2006, at 19:58, Parlamis Franklin wrote:
> i believe, if the function you are trying to work with has "..." as
> the first formal argument (as do most if not all of the "Summary"
> group functions), you will need to redefine the generic in order to
> provide a "real" S4 argument on which to dispatch.
>
> the following works for me (IIRC it was martin who initially pointed
> me in this direction, so any thanks are his).
>
> setGeneric("max", function(x, ..., na.rm = FALSE)
> {
> standardGeneric("max")
> },
> useAsDefault = function(x, ..., na.rm = FALSE)
> {
> base::max(x, ..., na.rm = na.rm)
> },
> group = "Summary")
>
> i don't have bleeding edge devel version installed, so i am not sure
> whether recent changes to S4 have mooted the above.
>
> (also, i thought i sent this last week, but i may have neglected to
> make it plain text, so maybe you didn't get it)
>
> franklin parlamis
>
> On Sep 4, 2006, at 3:47 AM, Robin Hankin wrote:
>
>> Hi everyone and thanks for being patient. I've used "!.foo"() et
>> seq pro tem.
>>
>> Next problem: how to define "Summary" methods for brobs.
>>
>> ?max says
>>
>> 'max' and 'min' are generic functions: methods can be defined for
>> them individually or via the 'Summary' group generic. For
>> this to
>> work properly, the arguments '...' should be unnamed.
>>
>> OK, so what is the correct procedure to make sum() operate on brob
>> objects?
>>
>> My best effort follows.
>>
[snipped]
--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre, Southampton
European Way, Southampton SO14 3ZH, UK
tel 023-8059-7743
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