Thank you for your adding, Steve, i followed Daivd's suggection and finally got the answer. It is my careless that should put lena instead of lenx. I also tried your codes and worked well. I appreciate your help. I learnt a lot from this forum.
Cheers, Zoe -- View this message in context: http://r.789695.n4.nabble.com/if-function-problems-tp3710995p3711340.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.
