[R] regex -> negate a word
Prof Brian Ripley
ripley at stats.ox.ac.uk
Mon Jan 19 11:32:40 CET 2009
On Mon, 19 Jan 2009, Rolf Turner wrote:
> On 19/01/2009, at 10:44 AM, Gabor Grothendieck wrote:
>> Well, that's why it was only provided when you insisted. This is
>> not what regexp's are good at.
>> On Sun, Jan 18, 2009 at 4:35 PM, Rau, Roland <Rau at demogr.mpg.de> wrote:
>>> Thanks! (I have to admit, though, that I expected something simple)
> It may not be what regexp's are good at, but the grep command in unix/linux
> does what is required *very* simply via the ``-v'' flag. I conjecture that
> it would not be difficult to add an argument with similar impact to the
> grep() function in R.
Indeed. I have often wondered why grep() returned indices, when a
logical vector would seem more natural in R (and !grep(...) would have
been all that was needed).
Looking at the code I see it does in fact compute a logical vector,
just not return it. So adding 'invert' (the long-form of -v is
--invert) is a job of a very few lines and I have done so for 2.9.0.
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
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