Thanks: [R] regexp problem on R 1.7.0

[Itay Furman]

Ooops. I missed that line, down there in the 'Examples', when I 
read the documentation. Sorry about that.

Thanks to Prof Brian Ripley and Gabor Grothendieck.

	Itay



On Tue, 30 Dec 2003, Gabor Grothendieck wrote:

> 
> 
> Just as an elaboration, this might help further clarify it.
> Spit displays each character in x -- one per line.
> 
> > spit <- function(x) for(i in 1:nchar(x)) cat(i,substring(x,i,i),"\n")
> > spit("e\+06") # note that the resulting string does not contain \
> 1 e 
> 2 + 
> 3 0 
> 4 6 
> > spit("e\\+06") # this time its there
> 1 e 
> 2 \ 
> 3 + 
> 4 0 
> 5 6 
>  
> Date: Tue, 30 Dec 2003 21:50:27 +0000 (GMT) 
> From: Prof Brian Ripley <ripley at stats.ox.ac.uk>
> To: Itay Furman <itayf at fhcrc.org> 
> Cc: <r-help at stat.math.ethz.ch> 
> Subject: Re: [R] regexp problem on R 1.7.0 
> 
>  
>  
> In R (and C) \ must be escaped in a character string.
> This is mentioned on the help page.
> 
> On Tue, 30 Dec 2003, Itay Furman wrote:
> 
> > 
> > Hi,
> > 
> > Am I missing something in using regexps in R?
> > Below, 'egrep' means invokation of the command from the shell 
> > prompt.
> > 
> > # I have
> > > as.character(block.dist.vals)
> > [1] "1e+06" "2e+06" "5e+06"
> > # that I wish to convert to: "1" "2" "5"
> > 
> > # OK (R and egrep)
> > > sub( "e.+06", "", as.character(block.dist.vals) )
> > [1] "1" "2" "5"
> > # OK (R), egrep will *not* match pattern
> > > sub( "e\\+06", "", as.character(block.dist.vals) )
> > [1] "1" "2" "5"
> > 
> > # egrep will match pattern; R will not.
> > > sub( "e\+06", "", as.character(block.dist.vals) )
> > [1] "1e+06" "2e+06" "5e+06"
> > 
> > As-far-as I can tell the last attempt should have worked, too.
> > Could someone explain to me why it doesn't?
> > 
> > I have R 1.7.0 on RedHat 9.
> > 
> > Thanks in advance,
> >      Itay Furman
> > 
> > =========================================================================
> >                Fred Hutchinson Cancer Research Center
> > email: itayf at fhcrc.org          1100 Fairview Avenue N., Mailstop D4-100
> > phone: +1 (206) 667 5921     P.O. Box 19024
> > fax: +1 (206) 667 2917     Seattle, WA 98109-1024
> > 
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> > 
> > 
> 
>