Dear Jun I think you should consider to submit your question to R-SIG (special interest group) about spatial data
http://r-sig-geo.2731867.n2.nabble.com/ This will improve the probability you get some help. Cheers Giuseppe Calamita ----- Giuseppe Calamita PhD at CNR-IMAA Italian National Council of Research - Institute of Methodologies for Environmental Analysis, Tito Scalo -Potenza ITALY -- View this message in context: http://r.789695.n4.nabble.com/Please-help-tp4635370p4635382.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.