Thank you very much Thomas! I indeed learned a lot. Baoqiang
On Tue, 2011-05-17 at 09:46 +1200, Thomas Lumley wrote: > } ______________________________________________ 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.
