spweights.constants function

Provides constants for spatial weights matrices

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).

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

Arguments

• listw: a listw object from for example nb2listw
• zero.policy: default attr(listw, "zero.policy") as set when listw was created, if attribute not set, use global option value; 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

Returns

• 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

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.

Author(s)

Roger Bivand Roger.Bivand@nhh.no

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")))