DanielFV <kalandru <at> hotmail.com> writes: [snip]
> I conducted GLS analyses introducing variance structures and correlation > structures to improve the model. > I plotted variograms before and after adding the correlation structures but > I would like to be able to conduct a test that gives me actual values for > spatial autocorrelation, so that I can show whether adding the correlation > structures improved significantly the model. > My variograms do not seem to improve after adding the correlation structures > so I don't know if I am conducting the right analyses. [snip] One thing to watch out for is that you want to extract the residuals with type="normalized" (see ?residuals.lme) (or use resType="normalized" in ACF() or Variogram: see ?acf.GLS, ?Variogram.GLS) -- otherwise, your residuals will be "pearson" type, corrected for non-homogeneous variance but not for correlation (I have fallen into this trap myself). Ben Bolker ______________________________________________ [email protected] 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.
