[R-sig-Geo] Test of independency in a contingency table for spatial variables

[Marcelino de la Cruz]

It seems to me that this can be analysed 
with  Syrjala's test [Syrjala, S. E. 1996, A 
Statistical Test for a Difference between the 
Spatial Distributions of Two Populations. Ecology, 77(1): 75-80]

I have some experimental code to run this test, in case you are interrested.

Regards,

Marcelino




At 22:03 02/04/2008, Agustin Lobo wrote:
>Dear list,
>
>I've classified a set of points according
>to two different sets of descriptors (assume
>a set of descriptors is biological, the other set environmental) into
>N and M classes respectively, thus I have
>2 vectors V1 and V2 recording each classification.
>I've made a contingency table
>conti <- table(V1,V2) of dimensions NxM
>
>summary(conti) provides the chi statistic
>to test for independence of both classifications,
>but, I suspect, if I'm classifying points
>the test should take spatial autocorrelation
>into account. Which test would be appropriate?
>The idea that comes to my mind is to randomize
>the values of the descriptors among the points
>and use a Monte Carlo approach. Is there any other
>way?
>
>Thanks!
>
>--
>Dr. Agustin Lobo
>Institut de Ciencies de la Terra "Jaume Almera" (CSIC)
>LLuis Sole Sabaris s/n
>08028 Barcelona
>Spain
>Tel. 34 934095410
>Fax. 34 934110012
>email: Agustin.Lobo at ija.csic.es
>http://www.ija.csic.es/gt/obster
>
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________________________________

Marcelino de la Cruz Rot

Departamento de  Biología Vegetal
E.U.T.I. Agrícola
Universidad Politécnica de Madrid
28040-Madrid
Tel.: 91 336 54 35
Fax: 91 336 56 56
marcelino.delacruz at upm.es