[R] Regular expressions

Ales Ziberna aleszib2 at gmail.com
Wed Jan 11 22:02:12 CET 2006

Thank you!

This is definitely an improvement! 

Ales Ziberna  

-----Original Message-----
From: pd at pubhealth.ku.dk [mailto:pd at pubhealth.ku.dk] On Behalf Of Peter
Sent: Wednesday, January 11, 2006 7:24 PM
To: Ales Ziberna
Cc: r-help at stat.math.ethz.ch
Subject: Re: [R] Regular expressions

"Ales Ziberna" <aleszib at gmail.com> writes:

> Matching regular expressions
> Dear useRs!
> I have the following problem. I would like to find objects in my 
> environment that have two strings in it. For example, I might want to 
> find objects that have in their names "MY" and "TARGET". I do not care 
> about the ordering of these two substrings in the name, neither what 
> is in front, behind or between them, the only thing important is that 
> both words are present. I apologize if this is covered in help pages 
> (then I did not understand it by reading them several times) or it was 
> answered previously (then I did not find it).
> Since "ls" with argument pattern essentially uses "grep" (if I am not 
> mistaken), I have an example for "grep"
> text<-c("somethigMYsomthing elseTARGET another thing","MY somthing 
> TARGET another thing","somethig somthing elseTARGETMY another 
> thing","somethigMTARGETY another thing")
> grep(pattern="MY&TARGET", x=text)
> #I would like to get 1 2 3  and not 4 or actually their names using 
> text[grep(pattern="MY&TARGET", x=text)] #of course, the "pattern" in 
> this case is wrong
> I know I can do
> text[grep(pattern="MY", x=text)][grep(pattern="TARGET", 
> x=text[grep(pattern="MY",x=text)])]
> However I hope there exists a more elegant way.

Perhaps this?

text[intersect(grep("MY",text), grep("TARGET",text))]

   O__  ---- Peter Dalgaard             ¨ster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)                  FAX: (+45) 35327907

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