spweights.constants {spdep} | R Documentation

## Provides constants for spatial weights matrices

### Description

The function calculates the constants needed for tests of spatial autocorrelation for general weights matrices represented as `listw` objects. Note: from spdep 0.3-32, the values of S1 and S2 are returned correctly for both underlying symmetric and asymmetric neighbour lists, before 0.3-32, S1 and S2 were wrong for listw objects based on asymmetric neighbour lists, such as k-nearest neighbours (thanks to Luc Anselin for finding the bug).

### Usage

    spweights.constants(listw, zero.policy=FALSE, adjust.n=TRUE)
    Szero(listw)

### Arguments

`listw` | a `listw` object from for example `nb2listw`
`zero.policy` | if TRUE ignore zones without neighbours, if FALSE fail when encountered
`adjust.n` | default TRUE, if FALSE the number of observations is not adjusted for no-neighbour observations, if TRUE, the number of observations is adjusted

### Value

`n` | number of zones
`n1` | n - 1
`n2` | n - 2
`n3` | n - 3
`nn` | n * n
`S0` | global sum of weights
`S1` | S1 sum of weights
`S2` | S2 sum of weights

### Author(s)

Roger Bivand Roger.Bivand@nhh.no

### References

Haining, R. 1990 Spatial data analysis in the social and environmental sciences, Cambridge University Press, p. 233; Cliff, A. D., Ord, J. K. 1981 Spatial processes, Pion, p. 19, 21.

### See Also

`nb2listw`

### Examples

    data(oldcol)
    B <- spweights.constants(nb2listw(COL.nb, style="B"))
    W <- spweights.constants(nb2listw(COL.nb, style="W"))
    C <- spweights.constants(nb2listw(COL.nb, style="C"))
    S <- spweights.constants(nb2listw(COL.nb, style="S"))
    U <- spweights.constants(nb2listw(COL.nb, style="U"))
    print(data.frame(rbind(unlist(B), unlist(W), unlist(C), unlist(S), unlist(U)),
      row.names=c("B", "W", "C", "S", "U")))

[Package spdep version 0.4-56 Index]