Re: [R] How to define S4 methods for '['

From: Gabor Grothendieck <ggrothendieck_at_gmail.com>
Date: Tue 21 Jun 2005 - 06:31:12 EST

On 6/20/05, Berton Gunter <gunter.berton@gene.com> wrote:
> Folks:
>
> This is a question about the S4 formal class system.
>
> Suppose I have a class, 'foo', defined by:
>
> setClass('foo',representation(dat='matrix', id='character') )
>
> I wish to define a '[' method for foo that will extract from the 'dat' slot.
> I would have thought that the following would work, but it doesn't:
>
> setMethod("[","foo",function(x,i, j, .,drop=TRUE)callGeneric(x@dat,i,
> j,drop=drop) )
>
> The only way I have succeeded in defining this method is using brute force
> eval(parse(. :
>
> {eval(parse(text=paste('.dat(x)[',
> ifelse(missing(i),',','i,'),
> ifelse(missing(j),']','j]'))))
> }
>
> This works. However, I am not able under any circumstances to pass the drop
> argument -- it is ignored.
>
> I would appreciate any pointers about how to do this properly. If this is
> explicitly in the Green Book (I do not have it with me at the moment), that
> will suffice.
>

Download the source to the 'its' package where an S4 [ method is defined.



R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Jun 21 06:37:26 2005

This archive was generated by hypermail 2.1.8 : Fri 03 Mar 2006 - 03:32:54 EST