st: Identify Neighbor Regions with Latitudes and Longitudes‏

[曦 田 <txsnowsea@hotmail.com>]

Dear Statalists,

I am working with a city level longitudinal data set for a large country. There are over 300 hundred cities for more than 20 years of observations in my data set. During the period,about 100 cities receive certain type of non reversible binary treatment. The effect of such treatment is what I am interested. To look at possible spillover effects, I would like to create a dummy indicate whether there are neighbor cities receiving similar treatment at the same time or before. I have basic geographic coordinates available, like latitudes and longitudes for each city used to draw the map. 
Is it possible to identify all neighboring cities, NOT the nearest cities with just latitudes and longitudes? If not, what other information I need to do the job?

Any suggestions would be much appreciated.

Thanks 
Tian 		 	   		  

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