[R] Flummoxed by gsub().

[Bert Gunter]

Inline.

-- Bert


Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Wed, Aug 23, 2017 at 2:29 AM, Rolf Turner <r.turner at auckland.ac.nz> wrote:
>
> On 23/08/17 18:33, Stefan Evert wrote:
>
>>
>>> On 23 Aug 2017, at 07:45, Rolf Turner <r.turner at auckland.ac.nz> wrote:
>>>
>>> My reading of ?regex led me to believe that
>>>
>>>     gsub("[:alpha:]","",x)
>>>
>>> should give the result that I want.
>>
>>
>> That's looking for any of the characters a, l, p, h, : .
>
>
> OK.  I see that now.  I don't think that it's really stated anywhere that to
> search for (and possibly change) any one of a string of characters you
> enclose that string of characters in brackets [  ].
>
> The first example from ?grep makes this "clear" (for some value of the word
> "clear") once you understand what this example is on about.
>
> So it's "obvious" once you've been shown, and totally opaque until then.

Well, "obviousness" is in the mind of the beholder, but, from ?regexp:

"A character class is a list of characters enclosed between [ and ]
which matches any single character in that list; "... (at the end of
the above section)

"For example, [[:alnum:]] means [0-9A-Za-z] "...

Note the doubled brackets. So seems pretty explicit to me.

Cheers,
Bert





>
>> What you meant to say was
>>
>>         gsub("[[:alpha:]]","",x)
>>
>> i.e. the character class [:alpha:] within a character set.
>
>
> Yup.  Got it.  Thanks very much.
>
> cheers,
>
> Rolf
>
> --
> Technical Editor ANZJS
> Department of Statistics
> University of Auckland
> Phone: +64-9-373-7599 ext. 88276
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.