[R] Pattern Matching help

[Prof Brian Ripley]

> From: Thomas Vogels <tov at ece.cmu.edu>
> Date: 17 Jan 2001 12:26:56 -0500
> 
> 
> Prof Brian Ripley <ripley at stats.ox.ac.uk> writes:
> 
> <snip>
> > `.' is a special character in a regexp.   You have to escape it by `\', and
> > that needs to be escaped in R.
> > 
> > Perhaps we need to say more on the help page, but I am reluctant to
> > try to define the meaning of `regular expression' there ....
> </snip> 
> 
> Since perl is a prerequisite for the installation of R, you might
> assume that its man pages are also available.  

Unfortunately it isn't, for a binary installation (and this was on Windows).

> 'man perlre' gives an
> overview of the special characters in the subsection "Regular
> Expressions".  So, could you refer the reader of the help page for
> gsub and friends to the man page of perlre?  (I don't what you would
> do for the Windows people...)

But these are POSIX not Perl regexps.  The latter are more powerful,
and have more special characters, AFAIK.


-- 
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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