[R] Test for multiple comparisons: Nonlinear model, autocorrelation?

Spencer Graves spencer.graves at pdf.com
Sat Jul 5 02:36:29 CEST 2008


  The question seems too general for me to offer specific suggestions.

What problem are you trying to solve that you think 'multiple 
comparisons' will answer?

Can you produce a similar problem that is completely self-contained 
example that eliminates complexity that may not be needed to understand 
your question (similar to the 'Auxiliary Problem' technique in "How to 
Solve It", http://en.wikipedia.org/wiki/How_to_Solve_It)? If you can, it 
may lead you to a solution. If you get such an example but still can't 
see a solution, send that example to this list (following the advice in 
the posting guide http://www.R-project.org/posting-guide.html). The 
simpler the example, the more likely someone on this list will reply 
quickly with a useful suggestion.

I know this doesn't solve your problem, but I hope it helps.
Spencer

J S wrote:
> Dear R community, 
>  
> I have a nonlinear model describing average daily soil temperature. What test should I use to compare differences in soil temperature of the two studied vegetation types depending upon month?
>  
> Building linear contrasts for the developed nonlinear model does not help since this model does not include variable “Months” (only “Days”). 
>  
> 1) Just a Student’s test is not probably an option because I would violate an assumption of independency, since the daily soil temperature observations have high autocorrelation. Or maybe I could average the observations for each month and then use this test since I have observations for a few years, and it might overcome the problem of independency?
>  
> 2) Should I develop a second nonlinear model with months instead of days, but it would considerably increase a number of parameters in the model...
>  
> Or:
> 3) ?
>  
> Thanks for your help,
> Julia
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