# spweights.constants

From spdep v0.6-9
by Roger Bivand

##### 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).

- Keywords
- spatial

##### Usage

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

##### Arguments

- listw
- a
`listw`

object from for example`nb2listw`

- zero.policy
- default NULL, 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

##### Value

##### 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

##### 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")))
```

*Documentation reproduced from package spdep, version 0.6-9, License: GPL (>= 2)*

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