Che-hsu (Joe) Chang wrote: > Hello everyone, > > > > I'm a new R user switching from SAS and JMP. In the first few days, I have > been trying to do a fairly simple task but yet found no success. I've > checked the help archive as well as few R textbooks but didn't seem to find > the answer. So, please help me if you can. > > > > Basically, I want to calculate the correlation between variable A and B for > every subject in my study. (yep, that simple) > > What I did is this: > > > > by(data, id, function (x) cor.test(A,B, data=x)) > > > > The results gave me numbers of correlation for each subject. But, the > problem is that, all these correlations are the same numbers and the sample > size was always the entire database (including all subjects). I've also > tried the lm function instead of the cor.test, and the by() function works > fine. Can any of you tell me what I did wrong? Or could you tell me what is > the best way to apply a function by subjects? Thank you! > > > > Only the model formula interface to cor.test uses the data argument, so you need either
cor.test(x$A,x$B) or cor.test(~A+B, data=x) > > > Best, > > Che-hsu (Joe) Chang, Sc.D., P.T. > > > > > -- O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ 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.
