I wonder why localmoran[,5] or P value which I get from R localmoran(variableX, weight.nb, alternative='two.sided') is different with GeoDa's (LISA_P). I have used alternative 'two.sided', 'greater', and 'less' but the they're still different. Both LISA indices from R and GeoDa are already equal. What should I do to get similar p value from R localmoran and GeoDa localmoran? Thanks ----- Ria Arinda Jakarta Institute of Statistics, Indonesia Tel: +62 856 1675312 -- View this message in context: http://r-sig-geo.2731867.n2.nabble.com/Why-do-I-get-different-P-value-of-LISA-from-R-and-GeoDa-tp7580621.html Sent from the R-sig-geo mailing list archive at Nabble.com.
Why do I get different P value of LISA from R and GeoDa ?
2 messages · ria arinda, Roger Bivand
On Fri, 27 Jul 2012, ria arinda wrote:
I wonder why localmoran[,5] or P value which I get from R localmoran(variableX, weight.nb, alternative='two.sided') is different with GeoDa's (LISA_P). I have used alternative 'two.sided', 'greater', and 'less' but the they're still different. Both LISA indices from R and GeoDa are already equal. What should I do to get similar p value from R localmoran and GeoDa localmoran? Thanks
If I remember correctly, GeoDa uses a permutation test (with random numbers), running only 99 permutations, while localmoran() in spdep uses the analytical expectations and variances. Repeated permutation tests and/or increasing the number of permutations should lead to similar results as the analytical formulae, possibly unless the data do not meet the distributional assumptions of the formulae. Try rather to use localmoran.sad() for a Saddlepoint approximation. Hope this clarifies, Roger
----- Ria Arinda Jakarta Institute of Statistics, Indonesia Tel: +62 856 1675312 -- View this message in context: http://r-sig-geo.2731867.n2.nabble.com/Why-do-I-get-different-P-value-of-LISA-from-R-and-GeoDa-tp7580621.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