From ripley at stats.ox.ac.uk  Tue Dec 13 19:10:14 2005
From: ripley at stats.ox.ac.uk (ripley@stats.ox.ac.uk)
Date: Tue, 13 Dec 2005 19:10:14 +0100 (CET)
Subject: [Rd] 0/1 vector for indexing leads to funny behaviour (PR#8389)
Message-ID: <20051213181014.703A4A21B@slim.kubism.ku.dk>

It is peculiar behaviour on your part, but the developers do not find it 
at all `funny'.

On Tue, 13 Dec 2005 rasche at molgen.mpg.de wrote:

> Full_Name: Axel Rasche
> Version: 2.2.0
> OS: Linux
> Submission from: (NULL) (141.14.21.81)
>
>
> Dear Debuggers,
>
> This is not a serious problem. Are 0/1 vectors intended to be used as index
> vectors? If yes, there is a bug. If not, it leads just to some funny behaviour
> rather than an error message.

They are, and in your example they work as documented.  You have not even 
told us what you think the bug is.

What happens in clearly stated in the R Language Definition and in all 
good reference books on R.

> In the appendix is some simple code to reproduce the problem. A logical vector
> as.logic(a) helps by indexing the vector b. The 0/1 vector a just returns the
> first value "a". But as many times as there is a 1 in a.

As it should.

>
> Best regards,
> Axel
>
>
> Appendix:
>
> b = c("a","b","c","d")
> a = c(0,1,1,0)
> b[as.logical(a)]
> b[a]
> a = c(1,0,1,0)
> b[as.logical(a)]
> b[a]
> a = c(0,1,1,1)
> b[as.logical(a)]
> b[a]


-- 
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)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595



[Rd] 0/1 vector for indexing leads to funny behaviour (PR#8389)
ripley@stats.ox.ac.uk