Eric,

The collapse command should do the trick. Depending on the structure of 
your data, you may need to do a reshape first.

A couple of things you might consider when planning your collapse:

Depending on precisely what you are trying to measure, it may make sense 
to consider each county to be its own neighbor as well.
Since counties are presumably of different sizes, a weighted average would 
probably be a good idea for any proportions.



=============================================
Moshe Haspel, Ph.D.
Assistant Professor, Department of Political Science
Spelman College
Giles 215
350 Spelman Lane SW, Box 207
Atlanta, GA  30314
404-270-5654 (phone)
404-270-5666 (fax)



eric magar <[log in to unmask]> 
Sent by: Political Methodology Society <[log in to unmask]>
09/29/2006 11:44 AM
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[POLMETH] Neighbours' average in stata






Dear colleagues:

I will be grateful for help on something that should be easy to
do in Stata but I am unfamiliar with. I have observations at the
county level and wish to compute the average value of certain
quantities of interest in neighbouring counties, such as the
average share of the two-party vote.

My dataset has info on which counties are neighbours, ie those
sharing a border with the current observation. This is coded as
a series of variables listing each a neighbouring county, in no
special order. Once the listing for a county is complete, the
remainder neighbour variables adopt missing values. A simple
example with four counties arranged in a line would be:

cty    vote  nei1  nei2
  1    0.45     2     .
  2    0.59     1     3
  3    0.51     4     2
  4    0.43     3     .

How can I get the average vote in neighbouring counties? My
dataset is quite large, so doing it case by case would take too
long.

Thank you and best wishes,

--e

______________________
Eric Magar
Ciencia Política, ITAM
Mexico City



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