[R] R: the spdep package

[Roger Bivand]

On Tue, 9 Dec 2003, Osmo Kolehmainen wrote:

> Hi,
> Here is a listw object z corresponding to the matrix W. I understand n, nn, 
> S0, S1 and S2 in the weights constants summary. Is it simply so that n1 = 
> n-1, n2 = n-2 and n3 = n-3? If this is true where they are needed?

Yes, used in calculating the variance of the statistics (Moran, Geary)  
elsewhere, are returned by spweights.constants(). Will be hidden in
summary.listw() in next release.

Roger

> Just wondering
> Osmo
> 
>  > W
> [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9]
> [1,] 0 1 0 1 0 0 0 0 0
> [2,] 1 0 1 0 1 0 0 0 0
> [3,] 0 1 0 0 0 1 0 0 0
> [4,] 1 0 0 0 1 0 1 0 0
> [5,] 0 1 0 1 0 1 0 1 0
> [6,] 0 0 1 0 1 0 0 0 1
> [7,] 0 0 0 1 0 0 0 1 0
> [8,] 0 0 0 0 1 0 1 0 1
> [9,] 0 0 0 0 0 1 0 1 0
>  > z=mat2listw(W);z
> Characteristics of weights list object:
> Neighbour list object:
> Number of regions: 9
> Number of nonzero links: 24
> Percentage nonzero weights: 29.62963
> Average number of links: 2.666667
> Weights style: M
> Weights constants summary:
> n n1 n2 n3 nn S0 S1 S2
> M 9 8 7 6 81 24 48 272
> 
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-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
e-mail: Roger.Bivand at nhh.no