localmoran {spdep}R Documentation

Local Moran's I statistic

Description

The local spatial statistic Moran's I is calculated for each zone based on the spatial weights object used. The values returned include a Z-value, and may be used as a diagnostic tool. The statistic is:

I_i = frac{(x_i-bar{x})}{{sum_{k=1}^{n}(x_k-bar{x})^2}/n}{sum_{j=1}^{n}w_{ij}(x_j-bar{x})}

, and its expectation and variance are given in Anselin (1995).

Usage

localmoran(x, listw, zero.policy=FALSE, spChk=NULL)

Arguments

x a numeric vector the same length as the neighbours list in listw
listw a listw object created for example by nb2listw
zero.policy if TRUE assign zero to the lagged value of zones without neighbours, if FALSE assign NA
spChk should the data vector names be checked against the spatial objects for identity integrity, TRUE, or FALSE, default NULL to use get.spChkOption()

Value

Ii local moran statistic
E.Ii expectation of local moran statistic
Var.Ii variance of local moran statistic
Z.Ii standard deviate of local moran statistic

Author(s)

Roger Bivand Roger.Bivand@nhh.no

References

Anselin, L. 1995. Local indicators of spatial association, Geographical Analysis, 27, 93–115; Getis, A. and Ord, J. K. 1996 Local spatial statistics: an overview. In P. Longley and M. Batty (eds) Spatial analysis: modelling in a GIS environment (Cambridge: Geoinformation International), 261–277.

See Also

localG

Examples

data(afcon)
oid <- order(afcon$id)
resI <- localmoran(spNamedVec("totcon", afcon), nb2listw(paper.nb))
print(data.frame(resI[oid,], row.names=afcon$name[oid]), digits=2)
resG <- localG(spNamedVec("totcon", afcon), nb2listw(include.self(paper.nb)))
print(data.frame(resG[oid], row.names=afcon$name[oid]), digits=2)


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