[R-sig-Geo] Weights based on a function and 'listw' object

[Roger Bivand]

On Thu, 12 Feb 2004, Virgilio Gómez Rubio wrote:

> Hi,
> 
> I am using a 'listw' object (see package spdep) to store weights to
> compute differentbstatistics, and I wonder whether it is possible to
> define weights as, say, the inverse of the distance (or any other
> function based on the centroids, for example).

See the example for nbdists(), and especially for nb2listw(), at the 
bottom, where the output from nbdists() is fed into nb2listw() through the 
glist= argument.

> 
> Futhermore, is it efficient to use one of these objects when
> all the areas are linked one another? Is it better to use a square nxn
> matrix in this case?
> 

Maybe, but you do lose the functions requiring a listw object, and you 
need to define the weighting style yourself (for example row 
standardised). In any case, weights at greater distances are very close to 
zero, so either distance bands or k-nearest neighbours will give very 
similar estimates (prove me wrong!!).

Roger

> Thank you for your help.
> 
> 

-- 
Roger Bivand
Econonic Geography Section, Department of Economics, Norwegian School of 
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen, 
Norway, voice: +47-55959355, fax: +47-55959393; Roger.Bivand at nhh.no