[R] Seeking help to define method for '+'

[Bogaso Christofer]

Thanks Martin for your help. Although your suggestion is working for
somewhat restrictive case, I would like to make thing more generic. For
example:

setMethod("Arith", c("Me", "Me"), function(e1, e2) callGeneric(e1 at x1,
e2 at x1))

with in (new1 + new2) is working perfectly, however if I want to add
arbitrary number of objects then it fails:

> new1 + new2 - new1
Error in new1 + new2 - new1 : non-numeric argument to binary operator

What can I do to handle this?

Thanks and regards,


-----Original Message-----
From: Martin Morgan [mailto:mtmorgan at fhcrc.org] 
Sent: 06 February 2011 03:57
To: Bogaso Christofer
Cc: r-help at r-project.org
Subject: Re: [R] Seeking help to define method for '+'

On 02/05/2011 02:19 PM, Bogaso Christofer wrote:
> Dear all, I am trying to define "+" method for my newly defined s4 class
> which is as follows:
> 
>  
> 
> setClass("Me", sealed=F,representation(x1 = "numeric", x2 = "character"))
> 
> new1 <- new("Me", x1=2, x2="comment1")
> 
> new2 <- new("Me", x1=3, x2="comment1")
> 
>  
> 
> setMethod("+", "Me", definition=function(x,y) cat(x at x1 + y at x1, "\n"))
> 
>  
> 
> However while am trying to set method, it fails:
> 
> Error in conformMethod(signature, mnames, fnames, f, fdef, definition) : 
> 
>   in method for '+' with signature 'e1="Me"': formal arguments (e1 = "Me",
> e2 = "Me") omitted in the method definition cannot be in the signature

From

> getGeneric("+")
standardGeneric for "+" defined from package "base"
  belonging to group(s): Arith

function (e1, e2)
standardGeneric("+", .Primitive("+"))
<environment: 0x19a9918>
Methods may be defined for arguments: e1, e2
Use  showMethods("+")  for currently available ones.

you can see that the generic is defined to dispatch on two arguments in
a signature function(e1, e2). So

  setMethod("+", c("Me", "Me"), function(e1, e2) e1 at x1 + e2 at x1)

but S4 also has group generics, and

  setMethod("Arith", c("Me", "Me"),
      function(e2, e2) callGeneric(e1 at x1, e2 at x1))

will define not just + but also - and other functions in the 'Arith'
group. See

  ?GroupGenericFunctions

Martin

> 
>  
> 
> I am just started learning s4 class system therefore please forgive me if
I
> have some any bad mistakes. Anyway I would really appreciate if someone
> point me how should I proceed.
> 
>  
> 
> Thanks and reagrds,
> 
> 
> 	[[alternative HTML version deleted]]
> 
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