[R] Inheriting from factors + co.
Torsten.Steuernagel at gmx.de
Tue Feb 24 18:59:05 CET 2004
I'm trying to create a formal class that does the following:
1) accept objects of arbitrary class as .Data slot
2) provide a set of other slots that are of fixed type (as usual)
The following two approaches came to my mind:
setClass("myclass", representation("ANY", x = "numeric", y
new("myclass", 1:10) # works
new("myclass", "Test") # works
new("myclass", factor(1:10)) # fails
While I'm able to specify any object that has a formal class as data part
it won't work with factors or other non-formal classes.
Since it is sufficient to use anything that inherits from "vector" and
"factor", I also tried the following one which seems to be cleaner than
using "ANY" directly.
setClassUnion("myunion", representation("vector", "factor")) #
setClass("myclass", representation("myunion", x="numeric",
new("myclass", 1:10) # fails
Now it isn't possible to assign anything as data part at all, as long as
the union contains any non-formal classes such as "factor". Replacing
"factor" with a formal class will do, of course.
I wonder if there is some way that does the trick because other
approaches aren't very straightforward. The obvious solution would be
a list as .Data part which can store anything but that isn't easy to
maintain. My goal is to have a formal class whose objects (i.e. .Data
part) can either be anything derived from "vector" or a factor (ordered).
I already played around with setIs() for implicit coercion but that doesn't
do anything as long as one of the classes is an S3 class.
Thanks for your help,
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