Thanks I agree i did not asked the question correctly, but I solved the issue using the suggestions from this post. http://www.mail-archive.com/r-help@stat.math.ethz.ch/msg23646.html -- View this message in context: http://r.789695.n4.nabble.com/grep-tp3004422p3006236.html Sent from the R help mailing list archive at Nabble.com.