On Jan 24, 2015, at 11:02 PM, Moxley, Jerad wrote: > Sorry I was not clearer, but I was asking an R programming question not a > theory question.
Copying back the original text which appears to have been omitted: On 25/01/2015 02:01, Moxley, Jerad wrote: > I’m trying to test what growth functions best fit individual subjects. I’m > wanting compare linear, quadratic, cubic etc. Here is the example from the > cubic curve. > > b3a<-by(c,id,function(x) lm(w~agec+ageq+agecub,data=x)) > I will try to clarify. If I did this analysis with a dataset involving just > one subject the summary command on the lm object would give me a significance > test on each parameter fit. The question in this cSe, is the cubic parameter > significant? It's not really true that you are "not asking a theory question". You do want inferences. A further problem might be that people who do statistics regularly would not be making statistical inferences based on naive construction of squared and cubed values. I suspect most readers would rather not comment on a procedure that seems particularly prone to invalid results. -- David. > When I try to do this for each subject separately in a larger dataset using > the by command, I get the parameter estimate but can't find a significance > test. I apologize again for my poor explanation originally, >> On Jan 24, 2015, at 10:04 PM, Jeff Newmiller <jdnew...@dcn.davis.ca.us> >> wrote: >> >> R-square is often a poor indicator of whether a model is appropriate or not. >> While it is possible that there exists a package that implements your >> algorithm (which you might find using the sos package), I would recommend >> that you get some advice from an expert on how to approach this subject, and >> this list is not a good place for studying statistics theory (read the >> Posting Guide). You might try stats.stackexchange. com. >> --------------------------------------------------------------------------- >> Jeff Newmiller The ..... ..... Go Live... > David Winsemius Alameda, CA, USA ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
