Message-ID: <Pine.LNX.4.44.0312081607300.19904-100000@gannet.stats>
Date: 2003-12-08T17:11:19Z
From: Brian Ripley
Subject: matrix coercion, logical -> character
In-Reply-To: <x2smjvpaeq.fsf@biostat.ku.dk>
On 8 Dec 2003, Peter Dalgaard wrote:
>
> Anyone know whether this is intentional, and by which rationale?
> (R-devel on RedHat, but hardly new)
It is documented:
'as.matrix' is a generic function. The method for data frames will
convert any non-numeric column into a character vector using
'format' and so return a character matrix.
Remember than not some long ago you could not have logical columns in data
frames: they were coerced to factors.
It would be easy to change to allow numeric, logical or character
matrices.
>
>
> > l <- data.frame(a=rpois(10,1)>0,b=rpois(10,1)>0)
> > apply(l,1,which)
> Error in FUN(newX[, i], ...) : argument to "which" is not logical
> > lapply(l,mode)
> $a
> [1] "logical"
>
> $b
> [1] "logical"
>
> > mode(as.matrix(l))
> [1] "character"
>
>
>
--
Brian D. Ripley, ripley@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