[R] S4 : defining [<- using inheritance from 2 classes

[Martin Morgan]

On 11/17/2011 09:46 PM, cgenolin wrote:
> Hi the list,
>
> I define a class 'C' that inherit from two classes 'A' and 'B'. 'A' and 'B'
> have no slot with similar names.
> ----------------
> setClass(
>      Class="C",
>      contains=c("A","B")
> )
>
>
> To define the get operator '[' for class "C", I simply use the get of "A" or
> "B" (the constante 'SLOT_OF_A' is a character holding the names of all the
> slot of A) :
> ----------------
> setMethod("[","C",
>    function(x,i,j,drop){
>       if(i%in%SLOT_OF_A){
>          x<- as(x,'A')
>       }else{
>          x<- as(x,'B')
>       }
>       return(x[i,j])
> }
> ----------------
>
> Is it possible to do something similar for the set operator '[<-' ?

Hi Christophe,

can you provide a working example? The above seems highly unusual; 
normally one expects class(x[i, j]) = class(x). Best guess at what 
you're wrote above is

setMethod("[", c("C", "character", "numeric"),
     function(x, i, j, ..., drop=TRUE) # conform to getGeneric("[")
{
     if (!i %in% slotNames(x))
         stop("cannot subset with '", i, "'")
     slot(x, i) = slot(x, i)[j]
     x
})

which still seems quite unusual.

Hope that helps,

Martin

>
> Thanks
> Christophe
>
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