[R-sig-Geo] Anselin Local Moran's I with R

Roger Bivand Roger.Bivand at nhh.no
Tue Sep 9 15:24:11 CEST 2014

On Tue, 9 Sep 2014, David Romero wrote:

> Hello,
> Could somebody help me with the method to compute the Cluster and Outlier
> Analysis using spdep and obtain Local I Index, Z-scores and cluster type
> like with the Arcgis tool.

Preferably not. The Arcgis tool answers lots of the wrong questions 
wrongly. If you take multiple comparisons seriously - see ?p.adjust - and 
treat permutations of all values except i to permutation bootstrap with 
reserve (use localmoran.sad() or localmoran.exact() instead), you'll 
realise that the z-scores are deceptive, and the "cluster" types (HH/LL, 
LH/HL) wrongheaded if you colour only "significant" ones - they are only 
significant in most cases before correcting for multiple comparisons. 
Further, if the mean model is mis-specified (yi - \bar{y} uses \bar{y} 
alone as the mean model), there may well not be any autocorrelation 
anyway, just omitted spatially patterned covariates.

> My data are points with temperature value.

In your case temperature should surely be related to elevation, and very 
likely to urban density before trying to measure local residual 
autocorrelation. Just because they do this in Arcgis, it doesn't mean that 
it is an appropriate procedure.

Hope this clarifies,


> Thank you,
> David Romero
> phD student
> Instituto de Geografía
> 	[[alternative HTML version deleted]]

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Roger Bivand
Department of Economics, Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 91 00
e-mail: Roger.Bivand at nhh.no

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