[R] regexp problem on R 1.7.0

[Prof Brian Ripley]

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
> 
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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 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595