[R] A clean way to initialize class slot of type "numeric" vector

Prof Brian Ripley ripley at stats.ox.ac.uk
Mon Aug 13 08:22:10 CEST 2007

Well, c() is NULL, so R did as you asked it to.  See ?integer: an integer 
vector of length 0 can be gotten by integer(0) (and other ways).

If you want integers, why have a slot which is numeric?

> setClass("foo", representation(members="integer"))
[1] "foo"
> new("foo")
An object of class "foo"
Slot "members":

is the natural and simpler way to do this.

On Mon, 13 Aug 2007, adschai at optonline.net wrote:

> Hi,
> I have a class definition like this:
> setClass("foo", representation(members="numeric"),
>   prototype(members=c()))
> I intend my class to have members, a slot whose value should be a vector 
> of integer. When I initialize this class, I don't have any member yet. 
> So my member is blank. But if I run the above definition into R, it will 
> complain that my slot members is assigned to NULL which does not extend 
> class "numeric". So how can I fix this? Is there any clean way to do 
> this? This is quite a common situation but I can't seem to find a way 
> out. Any help would be really appreciated. Thank you.
> - adschai
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Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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