localG {spdep} - critical values for Gi* statistics
On Wed, 21 Sep 2011, zbynek.janoska at centrum.cz wrote:
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.
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
Thank You, Zbynek -- View this message in context: http://r-sig-geo.2731867.n2.nabble.com/localG-spdep-critical-values-for-Gi-statistics-tp6819053p6819053.html Sent from the R-sig-geo mailing list archive at Nabble.com.
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Roger Bivand Department of Economics, NHH Norwegian School of Economics, Helleveien 30, N-5045 Bergen, Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43 e-mail: Roger.Bivand at nhh.no