Ok then this code didn't do what I wanted. I want "not including 'arg' before 
'.symptom'", not individual letters of "arg", but rather as a word.

Bill Dunlap suggested using invert=T, it works for single 1 condition, but not 
for 2 conditions here: not including "arg" before ".", but at the same time, 
does include ".symptom".

Any other suggestions would be appreciated

John




________________________________
From: Peter Langfelder <peter.langfelder@gmail.com>

Cc: Bernd Weiss <bernd.weiss@uni-koeln.de>; r-help@r-project.org
Sent: Thu, March 31, 2011 5:55:26 PM
Subject: Re: [R] regular expression


> Thanks Bernd! I tried your approach with my real example, sometimes it worked,
> sometimes it didn't. For example
>
> grep('[^(arg)]\\.symptom',"stomach.symptom",value=T)
> [1] "stomach.symptom"
>
> grep('[^(arg)]\\.symptom',"liver.symptom",value=T)
> character(0)
>
> I think both examples should return the text, but the 2nd example didn't.
>
> What was wrong here?

Operator error :) Since you exclude 'r' before the '.', liver.symptom
does not match the pattern.

Peter

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