Extracting matched expressions

[Hadley Wickham-2]

Hi all,

Is there a tool in base R to extract matched expressions from a
regular expression?  i.e. given the regular expression "(.*?) (.*?)
([ehtr]{5})" is there a way to extract the character vector c("one",
"two", "three") from the string "one two three" ?

Thanks,

Hadley

--
http://had.co.nz/

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[Gabor Grothendieck]

strapply in the gsubfn package can do that. It applies the indicated
function, here just c, to the back references from the pattern match
and then simplifies the result using simplify. (If you omit simplify
here it would give a one element list like strsplit does.)

library(gsubfn)
pat <- "(.*?) (.*?) ([ehtr]{5})"
strapply("one two three", pat, c, simplify = c)

See home page at: http://gsubfn.googlecode.com


On Sun, Nov 8, 2009 at 1:51 PM, Hadley Wickham <[hidden email]> wrote:

> Hi all,
>
> Is there a tool in base R to extract matched expressions from a
> regular expression?  i.e. given the regular expression "(.*?) (.*?)
> ([ehtr]{5})" is there a way to extract the character vector c("one",
> "two", "three") from the string "one two three" ?
>
> Thanks,
>
> Hadley
>
> --
> http://had.co.nz/
>
> ______________________________________________
> [hidden email] mailing list
> 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.
>

______________________________________________
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[jholtman]

Is this what you want:

> x <- 'xxxx xxxx one two three xxxx xxxx'
> y <- sub(".*?([^[:space:]]+)[[:space:]]+([^[:space:]]+)[[:space:]]+([ehrt]{5}).*",
+     "\\1 \\2 \\3", x, perl=TRUE)
> unlist(strsplit(y, ' '))
[1] "one"   "two"   "three"


On Sun, Nov 8, 2009 at 1:51 PM, Hadley Wickham <[hidden email]> wrote:

> Hi all,
>
> Is there a tool in base R to extract matched expressions from a
> regular expression?  i.e. given the regular expression "(.*?) (.*?)
> ([ehtr]{5})" is there a way to extract the character vector c("one",
> "two", "three") from the string "one two three" ?
>
> Thanks,
>
> Hadley
>
> --
> http://had.co.nz/
>
> ______________________________________________
> [hidden email] mailing list
> 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.
>

--
Jim Holtman
Cincinnati, OH
[phone]

What is the problem that you are trying to solve?

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[Hadley Wickham-2]

Thanks Jim - it's not elegant, but it works.  Instead of using space
as a delimiter, I used "\u001E" - it's the unicode record delimiter
character, and I figure there's less chance of a clash with a
character in the match.

Hadley

On Sun, Nov 8, 2009 at 1:40 PM, jim holtman <[hidden email]> wrote:

> Is this what you want:
>
>> x <- 'xxxx xxxx one two three xxxx xxxx'
>> y <- sub(".*?([^[:space:]]+)[[:space:]]+([^[:space:]]+)[[:space:]]+([ehrt]{5}).*",
> +     "\\1 \\2 \\3", x, perl=TRUE)
>> unlist(strsplit(y, ' '))
> [1] "one"   "two"   "three"
>
>
> On Sun, Nov 8, 2009 at 1:51 PM, Hadley Wickham <[hidden email]> wrote:
>> Hi all,
>>
>> Is there a tool in base R to extract matched expressions from a
>> regular expression?  i.e. given the regular expression "(.*?) (.*?)
>> ([ehtr]{5})" is there a way to extract the character vector c("one",
>> "two", "three") from the string "one two three" ?
>>
>> Thanks,
>>
>> Hadley
>>
>> --
>> http://had.co.nz/
>>
>> ______________________________________________
>> [hidden email] mailing list
>> 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.
>>
>
>
>
> --
> Jim Holtman
> Cincinnati, OH
> [phone]
>
> What is the problem that you are trying to solve?
>
> ______________________________________________
> [hidden email] mailing list
> 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.
>

--
http://had.co.nz/

______________________________________________
[hidden email] mailing list
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.