R help - Jun 2009 - using regular expressions to retrieve a digit-digit-dot structure from a string

Hi,

 

i need to recognize itemization structures in strings which follow the
format: "digit-digit-dot" like e.g.

 

1.

2.

19.

211.

 

Given the string " This happened in the 21. century." (the dot behind
21 is
used in German instead of 21st) I want know where the dots are but I do not
want the 21.-dot to be returned as well.

 

I am not good at regular expressions. How can I retrieve or recognize dots
excluding the digit-digit-dot structure?

 

TIA, Mark

 

-------------------------------

Mark Heckmann

+ 49 (0) 421 - 1614618

www.markheckmann.de

R-Blog:  <http://ryouready.wordpress.com> http://ryouready.wordpress.com

 


	[[alternative HTML version deleted]]

Try this:

x <- "This happened in the 21. century."
gregexpr("[[:digit:]]\\.", x)

This returns the position of the digit-dot in the string.

On Mon, Jun 8, 2009 at 11:15 AM, Mark Heckmann <mark.heckmann@gmx.de>
wrote:
> Hi,
>
>
>
> i need to recognize itemization structures in strings which follow the
> format: "digit-digit-dot" like e.g.
>
>
>
> 1.
>
> 2.
>
> 19.
>
> 211.
>
>
>
> Given the string " This happened in the 21. century." (the dot
behind 21 is
> used in German instead of 21st) I want know where the dots are but I do not
> want the 21.-dot to be returned as well.
>
>
>
> I am not good at regular expressions. How can I retrieve or recognize dots
> excluding the digit-digit-dot structure?
>
>
>
> TIA, Mark
>
>
>
> -------------------------------
>
> Mark Heckmann
>
> + 49 (0) 421 - 1614618
>
> www.markheckmann.de
>
> R-Blog:  <http://ryouready.wordpress.com>
http://ryouready.wordpress.com
>
>
>
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org 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.
>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

	[[alternative HTML version deleted]]

On Jun 8, 2009, at 9:15 AM, Mark Heckmann wrote:
> Hi,
>
>
>
> i need to recognize itemization structures in strings which follow the
> format: "digit-digit-dot" like e.g.
>
>
>
> 1.
>
> 2.
>
> 19.
>
> 211.
>
>
>
> Given the string " This happened in the 21. century." (the dot  
> behind 21 is
> used in German instead of 21st) I want know where the dots are but I  
> do not
> want the 21.-dot to be returned as well.
>
>
>
> I am not good at regular expressions. How can I retrieve or  
> recognize dots
> excluding the digit-digit-dot structure?
>
>
>
> TIA, Mark
>
vec <- c("1.", "2.", "19.", "211.",
"This happened in the 21. century")

 > grep("^[0-9]+\\.", vec, value = TRUE)
[1] "1."   "2."   "19."  "211."


The regex "^[0-9]+\\." is interpreted as "match one or more
digits
followed by a period, only at the beginning of the line".  The caret  
'^' defines the beginning of the line, so that a sequence of numbers  
followed by a period in the middle of the line will not match.

HTH,

Marc Schwartz

Try this.  See ?regex for more.
> x <- 'This happened in the 21. century." (the dot behind 21
is'
> regexpr("(?![0-9]+)[.]", x, perl = TRUE)
[1] 24
attr(,"match.length")
[1] 1


On Mon, Jun 8, 2009 at 10:15 AM, Mark Heckmann<mark.heckmann at gmx.de>
wrote:
> Hi,
>
>
>
> i need to recognize itemization structures in strings which follow the
> format: "digit-digit-dot" like e.g.
>
>
>
> 1.
>
> 2.
>
> 19.
>
> 211.
>
>
>
> Given the string " This happened in the 21. century." (the dot
behind 21 is
> used in German instead of 21st) I want know where the dots are but I do not
> want the 21.-dot to be returned as well.
>
>
>
> I am not good at regular expressions. How can I retrieve or recognize dots
> excluding the digit-digit-dot structure?
>
>
>
> TIA, Mark
>
>
>
> -------------------------------
>
> Mark Heckmann
>
> + 49 (0) 421 - 1614618
>
> www.markheckmann.de
>
> R-Blog: ?<http://ryouready.wordpress.com>
http://ryouready.wordpress.com
>
>
>
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org 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.
>