[R] S4 class questions

[Martin Morgan]

"Li, Xuejun" <XueLi at coh.org> writes:

>  
>
> Hi, I'd like to create a S4 class contains only one type of data.
> However, the number of slots varies.
>
> For example, I want to create a class "a", each slots in "a" contains
> numeric value only.  
>
>> setClass("a", contains = "numeric")
>
> If I want to create an object "a" with only one slot containing c(3,4),
> I will write
>
>> new("a", c(3,4))
>
> What if I want to create another object "a" with three slots with c(3,4)
> in the 1st slot, c(1,2) in the second, and c(0, 5) in the third?

Your class definition says that 'a' has just one slot, so you can't
have three slots. Maybe you want to create another class, or a little
class hierarchy,

setClass("a") # 'VIRTUAL'

setClass("a1, contains="a",
         representation=represention(
           a1="numeric"
         ))

setClass("a2, contains="a",
         representation=represention(
           a1="numeric",
           a2="numeric"
         ))

or maybe you want to create a class that that can contain a list of
numeric vectors, e.g.,

setClass("avector", contains="list",
         validity=function(object) {
             ok <- sapply(slot(object, ".Data"), is, "numeric")
             if (!all(ok)) "values must be numeric"
             else TRUE
         })

and then

> new("avector")
An object of class "avector"
list()
> new("avector", list(1:10, 5:1))
An object of class "avector"
[[1]]
 [1]  1  2  3  4  5  6  7  8  9 10

[[2]]
 [1]  5  4  3  2  1

> new("avector", list(1:10,letters))
Error in validObject(.Object) : 
  invalid class "avector" object: values must be numeric

Martin

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> Arthur Xuejun Li
>
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>
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-- 
Martin Morgan
Computational Biology / Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N.
PO Box 19024 Seattle, WA 98109

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