Hello,

form = ~ latitude + longitude

# using projected coordinates
# if a mixed model, you might want to specify the random effects structure 
by adding |'name of grouping factor'



HTH

Cheers,
Luca






------------------------------------------------------------------
Luca Borger (PhD, MSc, BMus)
Centre d'Etudes Biologiques de Chize
CNRS (U.P.R. 1934) & INRA (USC 1339)
79360 Villiers-en-Bois, France
*****
email: lborger@cebc.cnrs.fr
Skype: luca.borger | Tel: +33 (0)549 099613
http://cnrs.academia.edu/LucaBorger
http://www.researcherid.com/rid/C-6003-2008
http://www.cebc.cnrs.fr/Fidentite/borger/borger.htm
------------------------------------------------------------------
* new book chapter:
Borger & Fryxell (2012) Quantifying individual differences in dispersal 
using the net squared displacement statistics.
Ch. 17 In: Dispersal Ecology and Evolution. Editors: Clobert J., Baguette 
M., Benton T., Bullock J.
Oxford University Press, Oxford (UK).
-
-----Original Message-----
From: r-sig-geo-bounces@r-project.org 
[mailto:r-sig-geo-bounces@r-project.org] On Behalf Of Gabriel Gartner
Sent: Thursday, June 13, 2013 8:43 PM
To: r-sig-geo@r-project.org
Subject: [R-sig-Geo] specifying correlation structure in (n)lme

Hi All,

I have what I imagine is a fairly basic question, but I am a relative 
beginner at using spatial data in my analyses.  I am trying to address 
spatial autocorrelation in my data which examines lizard morphology across a 
broad geographic range.  My spatial data is in the form of decimal long/lat 
and I am trying to select which variogram model to use.

My question is, what is the form of the correlation structure within each of 
the corClasses for decimal lat/long data.  In other words, what goes after 
"form" in the following example script:

exp.cybotes<-update(null.model, correlation =corExp(1, form = ???), method= 
"ML")

I apologize for the basic question but I am stuck!

Thanks,
Gabriel


Gabriel E.A. Gartner
Postdoctoral Fellow
Museum of Comparative Zoology
Harvard University
26 Oxford St.
Cambridge, MA 02138
Office: 617-384-8437
http://www.oeb.harvard.edu/faculty/losos/Gartner/index_2.html 
[http://www.oeb.harvard.edu/faculty/losos/Gartner/index_2.html]
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