From plummer@iarc.fr  Wed Nov 18 17:22:23 1998
From: plummer@iarc.fr (Martyn Plummer)
Date: Wed, 18 Nov 1998 18:22:23 +0100
Subject: "[" not "[<-"
References: <199811181621.QAA20954@toucan.stats.ox.ac.uk> <98Nov18.115341est.13464@mailgate.bank-banque-canada.ca>
Message-ID: <3653024F.5325D12D@iarc.fr>

Paul Gilbert wrote:
> 
> Brian Ripley writes
> >on any of these, but it is less clear what [] should do. As it is not
> >clear if the attributes apply to the whole object only, I suspect stripping
> >is right.
> 
> I have played with this some and the answer is not obvious. There are some
> attributes it would be nice to keep and others it would be better to strip. My
> tframe attribute has to be consistent with the first dimension of the matrix, so
> it either has to be modified when the dim is modified or it has to be stripped
> so that there is not conflicting information. I have learned to live with the
> latter.

Couldn't you use the object-oriented features of R? For objects of class
"foo", subsetting can be done using the "[.foo" function. Attributes can be
saved
before passing the data on to NextMethod (which would strip attributes it
doesn't
know about). Then the saved attributes could be restored, possibly in a
modified
form, if the object is still of class "foo".

I had assumed that this was the logic of subsetting, but it would be nice
if someone could confirm this.

Martyn
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"[" not "[<-"
Martyn Plummer