Thanks I was looking at that package and reading your mails in the archive.
I think my tiny mind got twisted in the regexp..
On Wed, May 5, 2010 at 2:35 PM, Gabor Grothendieck
<ggrothendi...@gmail.com>wrote:
> Here are two ways to extract 5 digits.
>
> In the first one \\1 refers to the portion matched between the
> parentheses in the regular expression.
>
> In the second one strapply is like apply where the object to be worked
> on is the first argument (array for apply, string for strapply) the
> second modifies it (which dimension for apply, regular expression for
> strapply) and the last is a function which acts on each value
> (typically each row or column for apply and each match for strapply).
> In this case we use c as our function to just return all the results.
> They are returned in a list with one component per string but here
> test is just a single string so we get a list one long and we ask for
> the contents of the first component using [[1]].
>
> # 1 - sub
> sub(".*(\\d{5}).*", "\\1", test)
>
> # 2 - strapply - see http://gsubfn.googlecode.com
> library(gsubfn)
> strapply(test, "\\d{5}", c)[[1]]
>
>
>
> On Wed, May 5, 2010 at 5:13 PM, steven mosher <mosherste...@gmail.com>
> wrote:
> > Given a text like
> >
> > I want to be able to extract a matched regular expression from a piece of
> > text.
> >
> > this apparently works, but is pretty ugly
> > # some html
> >
> test<-"</tr><tr><th>88958</th><th>Abcdsef</th><th>67.8S</th><th>68.9\nW</th><th>26m</th>"
> > # a pattern to extract 5 digits
> >> pattern<-"[0-9]{5}"
> > # regexpr returns a start point[1] and an attribute "match.length"
> > attr(,"match.length)
> > # get the substring from the start point to the stop point.. where stop =
> > start +length-1
> >>
> >
> answer<-substr(test,regexpr(pattern,test)[1],regexpr(pattern,test)[1]+attr(regexpr(pattern,test),"match.length")-1)
> >> answer
> > [1] "88958"
> >
> > I tried using sub(pattern, replacement, x ) with a regexp that captured
> the
> > group. I'd found an example of this in the mails
> > but it didnt seem to work..
>
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