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RE: st: spatial weighting matrix


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: spatial weighting matrix
Date   Wed, 8 Apr 2009 18:56:41 +0100

I think that's all correct, but one extra detail may bite. For example,
a common size of problem is all 3000 or so counties in the USA. For
coding contiguities for that, you really need to have or to mimic sparse
matrix routines. 

Nick 
n.j.cox@durham.ac.uk 

Kyle Hood

Thanks for the explanation of queen - I do recall that chess references 
are used, now; I guess I had forgotten since I have never based a weight

matrix on contiguity.

I am a little confused about what the asker wants from Stata, here.  He 
says he has addresses (points), but wants a weighting matrix that 
depends on contiguity, which only makes sense for areal data.  If these 
addresses contain the areas in question (for example, zip codes or 
states) then no geocoding is necessary -- one must simply extract the 
areas from the address data.  However, after that, the information 
concerning which areas are adjacent to others is needed.  I can't 
imagine that Stata can be used to obtain this information.  If the asker

has this information already, then it would of course be trivial to 
program the weighting matrix in Stata (using Mata or not).

If the addresses do not contain the areas in question (for example, the 
asker wishes to consider adjacent census tracts, but has street address 
data), then the address information will have to be geocoded.  The 
geocoded data must then be matched up with a map of census tracts based 
on location.  In addition, information on which census tracts were 
adjacent would be needed, and this presents the same problem as above.

Some of this can be done in Stata, but there are pieces that other 
software is better suited to deal with.

Nick Cox wrote:
> The queen terminology in spatial analysis comes via chess. 
>
> Imagine squares on a chessboard. 
>
> A queen can enter a neighbouring square either across a length of
> boundary (over a link or edge in a boundary network) or diagonally (if
> two areas touch at a vertex or node in a boundary network). 
>
> A rook or castle is limited to the first of those. 
>
> In chess there are of course also other rules but they do not enter
> here. 
>
> Thus "queen" implies contiguity wide sense and "rook" strict sense. 
>
> The terminology goes back at least as far as the work of geographer
> Andrew Cliff and econometrician-statistician Keith Ord in the late
> 1960s. 
>
> In terms of the question, I implemented weighting matrices via string
> variables [!!!] in -spautoc- on SSC in 1997, but I'd do it in Mata
now,
> but I don't have detailed advice, let alone code. 
>
> Nick 
> n.j.cox@durham.ac.uk 
>
> Kyle Hood
>
>
> I'm not sure what "first-order queen contiguity" is, but you will 
> probably have to geocode address data (geocode: address->lat/lon), and
I
>
> don't think you can do this in Stata (that is, unless the breadth of 
> Stata's capabilities is larger than I had realized, which is sometimes

> the case).  Try ArcGIS.  Once you have the geocoded data, you can 
> probably compute the weight matrix in Stata, if you want.
>
> max r wrote:
>
>   
>> I need to create a spatial weighting matrix (first-order queen
>> contiguity) for a unbalanced panel dataset. The dataset has address
>> information in it. Is there a way to do this in STATA? I am trying to
>> test for neigborhood effects in behavior. Appreciate your thoughts.
>>     
>
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>   


-- 
Kyle Hood
Department of Economics
Yale University
New Haven, CT
website: http://www.econ.yale.edu/~kkh25/

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