
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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