Dear all,

I have a dataset with several lat-long coordinates (48) and corresponding residuals values (not a grid). Using the spdep package, I try to create a correlogram of these residuals according to several lags (i.e. distance classes) but I can’t seem to get the neighborhood and weights right…

Below, I show the main parts of the code and the results:

 rnp <- read.table ("D:/Diederik/RESID_WITH_DISTANCE.csv",sep=",",header=T)
 resids <- rnp$RESID
 
 ##create neighbourhood list and make symmetric##
 xy <- cbind(rnp$X, rnp$Y)
 rnp_nb <-knn2nb(knearneigh(xy, longlat=TRUE))
 rnp_nb <-make.sym.nb(rnp_nb)
 rnp_nb

Neighbour list object:
Number of regions: 48 
Number of nonzero links: 66 
Percentage nonzero weights: 2.864583 
Average number of links: 1.375 
 
 ##create weights##
 rnp_w <- nb2listw(rnp_nb,glist=NULL,style="W",zero.policy=FALSE)
 rnp_w

Characteristics of weights list object:
Neighbour list object:
Number of regions: 48 
Number of nonzero links: 66 
Percentage nonzero weights: 2.864583 
Average number of links: 1.375 

Weights style: W 
Weights constants summary:
   n   nn S0       S1       S2
W 48 2304 48 73.72222 209.3333
  
 ## Moran's I test for spatial autocorrelation##  
 moran.test(resids, rnp_w, randomisation=TRUE, …)

        Moran's I test under randomisation

data:  resids  
weights: rnp_w   
Moran I statistic standard deviate = -0.3353, p-value = 0.6313
alternative hypothesis: greater 
sample estimates:
Moran I statistic       Expectation          Variance 
      -0.08060979       -0.02127660        0.03130522 

 
 
 
 ##make a correlogram## 
 sp.correlogram(rnp_nb, resids, order=16, method="I", zero.policy=TRUE)

Error in nb2listw(nblags[[i]], style = style, zero.policy = zero.policy) : 
  No valid observations
In addition: Warning message:
In moran.test(var, listw, randomisation = randomisation, zero.policy = zero.policy) :
  Out-of-range p-value: reconsider test arguments


Moran.test seems to work fine, but the sp.correlogram doesn’t…  Do I – in any way- have to attach the weigths (rnp_w) to the neighourhood list (rnp_nb)?

Many thanks!!

Diederik

PS: R-version 2.9.2, Package spdep version 0.4-56, Windows Vista Home Premium Service Pack 2 on Acer Extensa 5630

Dr. Diederik Strubbe
Evolutionary Ecology Group
Department of Biology
University of Antwerp
Groenenborgerlaan 171
2020 Antwerpen, Belgium
tel: +32 3 265 3464


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