[Rd] replicating lists

[David James]

hi,

Yes, I agree that the work-around needs some care, but I'm not sure 
we need to wrap the list itself -- we're simply using properties of 
"[" on lists.  If the subscript is rep(1, 10), then we'll get the 
first element 10 times (which is *not* replicating the list).
To get the replication we need to index every element in 
the list as many times as required.

David

> Date: Wed, 11 Apr 2001 15:28:02 +0100 (BST)
> From: Jonathan Rougier <J.C.Rougier@durham.ac.uk>
> X-Sender: dma0jcr@laplace
> To: David James <dj@research.bell-labs.com>
> cc: r-devel@stat.math.ethz.ch
> Subject: Re: [Rd] replicating lists
> MIME-Version: 1.0
> 
> On Wed, 11 Apr 2001, David James wrote:
> 
> > A workaround is to use rep() inside "[":
> > 
> > > a <- list(a=1, b=2, c=3)
> > > a[rep(1:3, 1:3)]
> > $a
> > [1] 1
> > 
> > $b
> > [1] 2
> > 
> > $b
> > [1] 2
> > 
> > $c
> > [1] 3
> > 
> > $c
> > [1] 3
> > 
> > $c
> > [1] 3
> > 
> > Note, however, that names are no longer unique!
> 
> This work-around is cunning but needs a bit of care, as to get the
> replication of the whole of fred you need to wrap the list itself:
> 
> > fred <- list(happy = 1:10, fred = "squash")
> > list(fred)[rep(1, 10)] # list with 10 copies of fred
> 
> Cheers, Jonathn.
> 
> Jonathan Rougier                       Science Laboratories
> Department of Mathematical Sciences    South Road
> University of Durham                   Durham DH1 3LE
> tel: +44 (0)191 374 2361, fax: +44 (0)191 374 7388
> http://www.maths.dur.ac.uk/stats/people/jcr/jcr.html
> 

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