R help - Aug 2007 - A clean way to initialize class slot of type "numeric" vector

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

adschai at optonline.net writes:
> 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.
How about:

  setClass("foo", representation(members="numeric"),
           prototype(members=numeric(0)))

That is, use a zero-length vector to signify a vector that isn't
there.

+ seth

-- 
Seth Falcon | Computational Biology | Fred Hutchinson Cancer Research Center
BioC: http://bioconductor.org/
Blog: http://userprimary.net/user/

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":
integer(0)

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)
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