[R] user-defined spatial correlation structure in geeglm/geese

From: Swantje Löbel <swantje.lobel_at_ebc.uu.se>
Date: Wed 08 Jun 2005 - 03:04:04 EST


Dear all,  

We have got data (response and predictor variables) for each country of the world; I started by fitting standard GLM and tested for spatial correlation using variogram models (geoR) fitted to the residuals of the GLM. Spatial autocorrelation is significant. Therefore, I think about using general estimation equations (geeglm or geese in geepack) allowing for residual spatial correlation . Several questions:  

  1. Are GEE’s the right choice?
  2. How can I specify a user-defined spatial (exponential) correlation structure in geeglm or geese? I did not really get this from the help-sites. I guess I need to set corstr = "userdefined" and zcor = Zcor, with Zcor being in some way the specified correlation matrix – but how? I earlier specified spatial exponential correlation structures in glmmPQL, but it seems that this does not work in the same way for geeglm or geese. Do I need to use the function genZcor?
  3. Makes it sense to use continents to specify clusters? Or is the number of clusters (8) too low?

I am grate-full for any comments!  

Thank you in advance,
Swantje    

Swantje Löbel

PhD student  

Department of Plant Ecology

Evolutionary Biology Centre (EBC)

Uppsala University

Villavägen 14

SE-752 36 Uppsala

Sweden  

Tel. +46 18 471 28 70

Fax +46 18 55 34 19  

http://www.vaxtbio.uu.se/resfold/lobel.htm  

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