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localG {spdep} - critical values for Gi* statistics

2 messages · zbynek.janoska at centrum.cz, Roger Bivand

zbynek.janoska at centrum.cz
# 
Hello,
I am wondering, if it is posiible to obtain critical values for Gi
statistics calculated by localG {spdep} function.

In manual there is (quoting): The critical values of the statistic under
assumptions given in the references for the 95th percentile are for n=1:
1.645, n=50: 3.083, n=100: 3.289, n=1000: 3.886.

However, I have n=77, right in the middle between values given, and also I
wonder, whether critical values for Gi* and Gi are the same? I suppose they
are, since the difference is only in spatial weights, is it not?
Consequently, another percentile than 95th could be useful.

Thank You,
Zbynek

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Roger Bivand
#
On Wed, 21 Sep 2011, zbynek.janoska at centrum.cz wrote:

            

      
      
      
    

        
The help page does point to the references, so they are where you should 
go. I'm not aware of anything else in the literature, but see:

Tonglin Zhang, Limiting distribution of the G statistics, Statistics and 
Probability Letters 78 (2008) 1656?1661

In any case, the p-values you are looking for will need Bonferroni or 
other adjustment, and as Zhang notes, when there are few neighbours, the 
assumption of normality will probably fail. The local Moran's I case is 
known in more detail, see Tiefelsdorf (2000) and papers citing his 
monograph.

Hope this helps,

Roger