[R] RegExp Question

[Prof Brian Ripley]

On Wed, 15 Aug 2001, Peter Malewski wrote:

>
> I've already a solution just the question: is this
>
> > gsub("[A-Z]","\#",c("1","2",NA,"B"))
> [1] "1"  "2"  "##" "#"
>                ^^
>                ^^
> intended (handlings NA: yes I know that
>
> > is.na(c("a",NA)[2])
> [1] TRUE
> > is.character(c("a",NA)[2])
> [1] TRUE
>
> )?

I believe so. The argument is internally coerced to C-style character
strings, and indeed your string is printed as such:

> c("1","2",NA,"B")
[1] "1"  "2"  "NA" "B"

NA could have been handled exceptionally, but it was not.


>
>
> PM
>
> On Wed, Aug 15, 2001 at 11:57:56AM +0200, Peter Malewski wrote:
> > On Wed, Aug 15, 2001 at 11:52:07AM +0200, Peter Dalgaard BSA wrote:
> > > Peter Malewski <peter.malewski at gmx.de> writes:
> > >
> > > > gsub("F\.","d",c("F123","F.123"),extended=F)
> > > > [1] "d23"  "d123"
> > > >
> > > > the problem is that the "F123" string is replaced (escaping "."
> > > > does not work??). What can I do?
> > >
> > > Escape more:
> > >
> > > > gsub("F\\.","d",c("F123","F.123"),extended=F)
> > > [1] "F123" "d123"
> > >
> > > Notice that
> > >
> > > > "F\."
> > > [1] "F."
> > >
> >
> > Thanks.
> > P.
> >
> > --
> > P.Malewski, Limmerstr.47, 30451 Hannover, 0511-2135008
> > At work: http://www.MH-Hannover.de 0511 532 3194 / Fax: 0511 532 3190,
> > P.Malewski at tu-bs.de, peter.malewski at gmx.de, malewski.peter at mh-hannover.de.
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> --
> P.Malewski, Limmerstr.47, 30451 Hannover, 0511-2135008
> At work: http://www.MH-Hannover.de 0511 532 3194 / Fax: 0511 532 3190,
> P.Malewski at tu-bs.de, peter.malewski at gmx.de, malewski.peter at mh-hannover.de.
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-- 
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 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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