On 26-Oct-09 09:44:55, ms.com wrote: > > Dear all > I am trying to learn R > I was trying to calculate standard deviation > here are the commands and outputs in R >> sd(Ht_cm[type=='SD'])[1] 3.283605 >> sd(Ht_cm[from_treeline=='above'])[1] 16.83289 >> sd(Ht_cm[type=='SD'][from_treeline=='above'])[1] NA > > the problem is that, i could not understand why the third command could > not give any result. > please help me out > thanking you > Regard > MS > Nepal
This suggests that either you have only one observation in the third case, or there is an NA amongst them. What are the values of length((Ht_cm[type=='SD'][from_treeline=='above'])[1]) sum(is.na((Ht_cm[type=='SD'][from_treeline=='above'])[1])) sum((type=='SD')&(from_treeline=='above')) sum(type=='SD') sum(from_treeline=='above') The answers to these may provide adequate clues to diagnose the reason. Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <ted.hard...@manchester.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 26-Oct-09 Time: 14:28:38 ------------------------------ XFMail ------------------------------ ______________________________________________ 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.
