>>>>> "BDR" == Prof Brian Ripley <[EMAIL PROTECTED]>
>>>>> on Fri, 25 Aug 2006 12:56:17 +0100 (BST) writes:
BDR> Just like any other S4 method: setMethod("+",
BDR> c("track", "track"), function(e1, e2) new("track",
BDR> x=c([EMAIL PROTECTED], [EMAIL PROTECTED]), y=c([EMAIL
PROTECTED],[EMAIL PROTECTED])))
BDR> If you want to write a group generic for the S4 Ops
BDR> group, you do it very like S3. There are worked
BDR> examples in 'S Programming' (that at least at one point
BDR> worked in R).
Indeed.
The 'Matrix' package has examples for both:
Most of the time, we define group generics for "Arith",
but we have one method for "+" (for "dgTMatrix" operands, where
"+" can be done in particular way).
Inside a source version of Matrix, use
grep 'setMethod("Arith"' R/*.R
or grep 'setMethod("+"' R/*.R
to find them.
Also look at NAMESPACE and R/AllGeneric.R
Martin Maechler, ETH Zurich
BDR> On Fri, 25 Aug 2006, Robin Hankin wrote:
>> Hi
>>
>> I'm trying to implement S4 methods in a package, and I am
>> having difficulty defining "+" to do what I want.
>>
>> In the Green Book, there is a discussion of a "track"
>> object,
>>
>> setClass("track", representation(x="numeric",
>> y="numeric"))
>>
>> OK.
>>
>> track1 <- new("track",x=c(1,4,6),y=c(10,11,12)) track2 <-
>> new("track",x=c(2,5),y=c(100,101))
>>
>>
>> What I want to do is to define "+" for track object so
>> that if
>>
>> track3 <- track1 + track2
>>
>> has [EMAIL PROTECTED] == c(1,2,4,5,6) and [EMAIL PROTECTED] =
>> c(10,100,11,101,12)
>>
>> maybe adding a track object to a scalar would shift the
>> values of the x slot.
>>
>> The algorithm itself is no problem...but what is the S4
>> equivalent to the S3 technique of writing an Ops.track()
>> function that tells R what "+" means?
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> --
>> Robin Hankin Uncertainty Analyst National Oceanography
>> Centre, Southampton European Way, Southampton SO14 3ZH,
>> UK tel 023-8059-7743
>>
>> ______________________________________________
>> R-devel@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>
BDR> -- Brian D. Ripley, [EMAIL PROTECTED] Professor of
BDR> Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
BDR> University of Oxford, Tel: +44 1865 272861 (self) 1
BDR> South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG,
BDR> UK Fax: +44 1865 272595
BDR> ______________________________________________
BDR> R-devel@r-project.org mailing list
BDR> https://stat.ethz.ch/mailman/listinfo/r-devel
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