---------- Original Message -----------
From: Duncan Temple Lang <[EMAIL PROTECTED]>
To: Ulrike Grömping <[EMAIL PROTECTED]>
Cc: Uwe Ligges <[EMAIL PROTECTED]>, r-help@stat.math.ethz.ch
Sent: Fri, 18 Nov 2005 10:26:51 -0800
Subject: Re: [R] Method for $
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> Ulrike Grömping wrote:
> > Uwe,
> >
> > thank thank you very much for your suggestion. This does in fact work, if I
> > define
> >
> > "$.myclass"<-function(x,slotname){slot(x,slotname)}
> >
> > which solves my immediate need.
> >
> > However, the setMethod version
> > setMethod("$", signature(x="myclass"), function(x,slotname){
> > slot(x,slotname)
> > }
> > )
> > still produces the same error message as before (cf. below). If anyone has
> > a
> > solution for this, I would appreciate it.
> >
>
> For the record, the problem you are experiencing is that
> you are not using the same argument names in your
> method as the function "$" uses. Hence there is a mismatch.
> Use
> setMethod("$", signature(x="myclass"), function(x, name){
> slot(x, name)
> } )
>
> i.e. rather than slotname as the second argument, use name
> as that is what $ uses.
Thanks very much for clarifying that. I just wasn't aware of the argument names
of $. It's obvious from the help file, once you know what to look for, but ...
>
> But, as Martin pointed out, this is not an advisable thing
> to do.
> And if you want to use an S4 class to house sub-elements,
> either explicitly specify their types with
> setClass('myclass', representation( a = "integer",
> b = "matrix", ....)
>
> or if you want them to be arbitary objects, then think
> about why you are using S4.
I have in fact used a class definition like the one you suggest, i.e. have
switched from a list to a class by defining an object type for each of my list
elements. As a consequence, the former list elements were no longer accessible
via "$", which is what I want to recover.
>
> > Uwe, my best wishes also to Dortmund and Lena, and by the way, it's your
> > book
> > that got me started with understanding (part of) the programming aspects of
> > R
> > relatively fast.
> >
> > Regards,
> > Ulrike Grömping
> >
> > ---------- Original Message -----------
> > From: Uwe Ligges <[EMAIL PROTECTED]>
> > To: Ulrike Grömping <[EMAIL PROTECTED]>
> > Cc: r-help@stat.math.ethz.ch
> > Sent: Fri, 18 Nov 2005 17:45:40 +0100
> > Subject: Re: [R] Method for $
> >
> >
> >>Ulrike Grömping wrote:
> >>
> >>
> >>>Dear R experts,
> >>>
> >>>I have defined a class "myclass" and would like the slots to be
> >
> > extractable
> >
> >>>not only by "@" but also by "$". I now try to write a method for "$" that
> >>>simply executes the request [EMAIL PROTECTED], whenever someone calls
> >>>object$slotname for any object of class "myclass".
> >>>I don't manage to find out how I can provide this function
> >
> > with "slotname",
> >
> >>>so that one and the same function works for any arbitrary slotname a user
> >>>might choose.
> >>>
> >>>I have tried
> >>>
> >>>setMethod("$", signature(x="myclass"), function(x,slotname){
> >>> [EMAIL PROTECTED]
> >>> }
> >>>)
> >>
> >>Ulrike,
> >>
> >>what about (untested!):
> >>slot(x, slotname)
> >>
> >>Best wishes from Dortmund and Lena,
> >>Uwe Ligges
> >>
> >>
> >>>This produced the error message:
> >>>In method for function "$": expanding the signature to
> >>>include omitted arguments in definition: name = "missing"
> >>>Error in rematchDefinition(definition, fdef, mnames, fnames, signature) :
> >>> methods can add arguments to the generic only if '...' is an
> >
> > argument
> >
> >>>to the generic
> >>>
> >>>My searches for a solution of this problem have not been successful. Can
> >>>someone help?
> >>>
> >>>Thanks and regards,
> >>>Ulrike Grömping, Berlin
> >>>
> >>>______________________________________________
> >>>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
> > ------- End of Original Message -------
> >
> > ______________________________________________
> > 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
>
> - --
> Duncan Temple Lang [EMAIL PROTECTED]
> Department of Statistics work: (530) 752-4782
> 371 Kerr Hall fax: (530) 752-7099
> One Shields Ave.
> University of California at Davis
> Davis, CA 95616, USA
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