R help - Nov 2015 - Extracting part of alpha numeric string

Hey,

worked like a charm! :)

Could you please explain about

sub("^([0-9]*).*$", "\\1", fields)

Thanks,
Abhinaba

On Mon, Nov 30, 2015 at 4:47 PM, <phgrosjean at sciviews.org> wrote:
> fields <- c("2154333b-3208-4519-8b76-acaef5b5a479",
> "980958a0-103b-4ba9-afaf-27b2f5c24e69",
>             "00966654-0dea-4899-b8cf-26e8300b262d")
> sub("^([0-9]*).*$", "\\1", fields)
>
> Best,
>
> Philippe Grosjean
>
> > On 30 Nov 2015, at 11:39, Abhinaba Roy <abhinabaroy09 at
gmail.com> wrote:
> >
> > Hi,
> >
> > I have a field with alpha numeric codes like,
> >
> > 2154333b-3208-4519-8b76-acaef5b5a479
980958a0-103b-4ba9-afaf-27b2f5c24e69
> > 00966654-0dea-4899-b8cf-26e8300b262d
> > I want a derived field which will contain ONLY the numeric part before
> the
> > first alphabet and the first '-',
> >
> > for example the derived field from the sample above will give me
> >
> > 2154333
> > 980958
> > 00966654
> >
> > How can this be achieved in R?
> >
> > P.S. I do not have much knowledge on regex. It would be of great help
if
> > you could suggest some reading for beginners.
> >
> > Thanks,
> > Abhinaba
> >
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > 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.
>
>
	[[alternative HTML version deleted]]

> Could you please explain about
> 
> sub("^([0-9]*).*$", "\\1", fields)
See ?regex and the extensive online literature on regular expressions.

S Ellison




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> On 30 Nov 2015, at 13:09, Abhinaba Roy <abhinabaroy09 at gmail.com>
wrote:
> 
> Hey,
> 
> worked like a charm! :)
> 
> Could you please explain about
> 
> sub("^([0-9]*).*$", "\\1", fields)
> 
Yes.

sub() replaces substrings. The first argument captures the interesting part of
the string:

^ = start of the string,

([0-9]*) = capture of the interesting part of the string. [0-9] means any figure
from 0 to 9. * means 1 or more of these characters, and () is used to capture
the substring,

.* = all the rest. Dot (.) means any character, and * means again one or more of
these characters,

$ = the end of the string.

The whole regular expression matches the whole string and captures the
interesting part inside the ().

The second argument is the replacement. //1 means the first captured substring.

Thus, globally, we replace the whole string by the captured substring.

Best,

Philippe Grosjean

> Thanks,
> Abhinaba
> 
> On Mon, Nov 30, 2015 at 4:47 PM, <phgrosjean at sciviews.org
<mailto:phgrosjean at sciviews.org>> wrote:
> fields <- c("2154333b-3208-4519-8b76-acaef5b5a479",
"980958a0-103b-4ba9-afaf-27b2f5c24e69",
>             "00966654-0dea-4899-b8cf-26e8300b262d")
> sub("^([0-9]*).*$", "\\1", fields)
> 
> Best,
> 
> Philippe Grosjean
> 
> > On 30 Nov 2015, at 11:39, Abhinaba Roy <abhinabaroy09 at gmail.com
<mailto:abhinabaroy09 at gmail.com>> wrote:
> >
> > Hi,
> >
> > I have a field with alpha numeric codes like,
> >
> > 2154333b-3208-4519-8b76-acaef5b5a479
980958a0-103b-4ba9-afaf-27b2f5c24e69
> > 00966654-0dea-4899-b8cf-26e8300b262d
> > I want a derived field which will contain ONLY the numeric part before
the
> > first alphabet and the first '-',
> >
> > for example the derived field from the sample above will give me
> >
> > 2154333
> > 980958
> > 00966654
> >
> > How can this be achieved in R?
> >
> > P.S. I do not have much knowledge on regex. It would be of great help
if
> > you could suggest some reading for beginners.
> >
> > Thanks,
> > Abhinaba
> >
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help at r-project.org <mailto:R-help at r-project.org> mailing
list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
<https://stat.ethz.ch/mailman/listinfo/r-help>
> > PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
<http://www.r-project.org/posting-guide.html>
> > and provide commented, minimal, self-contained, reproducible code.
> 
> 

	[[alternative HTML version deleted]]

> On 30 Nov 2015, at 14:57, phgrosjean at sciviews.org wrote:
> 
> 
>> On 30 Nov 2015, at 13:09, Abhinaba Roy <abhinabaroy09 at
gmail.com> wrote:
>> 
>> Hey,
>> 
>> worked like a charm! :)
>> 
>> Could you please explain about
>> 
>> sub("^([0-9]*).*$", "\\1", fields)
>> 
> 
> Yes.
> 
> sub() replaces substrings. The first argument captures the interesting part
of the string:
> 
> ^ = start of the string,
> 
> ([0-9]*) = capture of the interesting part of the string. [0-9] means any
figure from 0 to 9. * means 1 or more of these characters, and () is used to
capture the substring,
> 
> .* = all the rest. Dot (.) means any character, and * means again one or
more of these characters,
> 
> $ = the end of the string.
Small correction:

* means zero or more characters

according to ?regex.

Berend