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

[Martin Morgan]

On 02/05/2011 02:58 PM, Bogaso Christofer wrote:
> 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

as written, new1 + new2 returns a numeric, so (new1 + new2) - new1 would
require a method with signature c("numeric", "Me"). But perhaps what you
want is an implementation along the lines of

  setMethod(Arith, c("Me", "Me"), function(e1, e2) {
      new("Me", x1=callGeneric(e1 at x1, e2 at x2)
          x2=c(e1 at x2, e2 at x2))
  })

i.e., return an instance of "Me".

Martin

> 
> 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]]
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
> 
> 


-- 
Computational Biology
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N. PO Box 19024 Seattle, WA 98109

Location: M1-B861
Telephone: 206 667-2793