[R] Alternative options: nonlinear model &autocorrelation?

From: J S <yulya258_at_gmail.com>
Date: Fri, 30 May 2008 09:58:20 -0400


Dear R community,

Using nlme library I have developed a nonlinear mixed model. Incorporating an autoregressive model gives me an error that I can't allocate vector of size X. The problem is that my computer does not have enough physical memory most probably due to a large number of observations (17,000).

I was wondering what alternative options I might use:

  1. To use ARIMA and calculate residuals, and then to apply my nonlinear model to the residuals. I have a feeling it does not sound reasonable.
  2. If I could reduce the number of observations, my original plan would work well and I would not have a problem with physical memory. How to reduce the number of observations? My data consist of six sites with two plots per site. A) To average data from two plots? It seems to me we can loose some information; B) To model the effect of plots and remove it from the observations, then to average the residuals for two plots within each of the sites and apply the nonlinear model?

Your suggestions are appreciated.

Thanks,

Julia

PS: My data are daily data of soil temperature for six years, six sites and two plots per site.

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