[Rd] S4 methods for "+"

[Robin Hankin]

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 track3 at x  == c(1,2,4,5,6)
and
track3 at y = 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