[R-sig-Geo] newbie: Moran's I

Jeffrey Stratford stratja at auburn.edu
Fri Nov 3 13:21:37 CET 2006


Hi.

Does anyone have an example of estimating Moran's I from a file with
point (not polygon) data?  I'm getting close(r) but I still have a few
problems.

Here's my code so far:

library(spdep)
ctpoints <- read.csv("c:\\Georgia\\xy.csv", header=TRUE)
# only two columns containing the long-lat data 
str(ctpoints)
plot(ctpoints)
neigh <- tri2nb(ctpoints)
plot (neigh, ctpoints)
nblist <- nb2listw(neigh, glist=NULL, style="W", zero.policy=FALSE)
????? <- spNamedVec("?????", ctpoints)
gamoran <- moran(?????, nblist, n, S0, zero.policy=FALSE, NAOK=FALSE)   
 

I'm not sure what goes where I have "?????".  And yup, I did a
help(spNamedVec) but I'm not sure how to translate that material to my
case.  

Eventually, I would like to run a number of Poisson or negative binomial
regressions linking avian species richness to landscape variables around
the same points where I surveyed birds. See
http://web6.duc.auburn.edu/~stratja/georgia.pdf (map showing points on a
LANDSAT map) to get an idea of the proximity and location of points.
Since I will eventually incorporate spatial effects into my regressions
should I change the file to one that contains the coordinates, the bird
data, and the landscape data? 

Many thanks (again),

Jeff

****************************************
Jeffrey A. Stratford, Ph.D.
Postdoctoral Associate
331 Funchess Hall
Department of Biological Sciences
Auburn University
Auburn, AL 36849
334-329-9198
FAX 334-844-9234
http://www.auburn.edu/~stratja




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