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Re: st: Constructing assignment var for Spatial RDD: For each id in region 1 need shortest distance to an id in region 0


From   Roy Wada <roywada@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Constructing assignment var for Spatial RDD: For each id in region 1 need shortest distance to an id in region 0
Date   Fri, 27 Nov 2009 20:19:54 -0800

> I just haven't been able to figure out how to restrict it to search
> for the each member of group 0 (1) not the closest one of all but the
> closest one only from the respective other group, since -nearest-
> doesn't seem to allow if conditions.

I probably should have added a few more thing. -nearest- is written by
Nick Cox. Not allowing [if] [in] was probably intentional. People will
obviously try to use it that way, not realizing it will apply to the
entire sample.

I hope you are pre-multiplying the longitude or latitutde by a factor
of 60.9 or something. Otherwise you are dealing with a
squashed-looking map. If you want a geographical distance, try
-distmatch- from ssc.. It has a one-direction mapping via -donor( )-
and -recipient( )- options. There is also -vincent- by Austin Nichols
that you may want to check.

Roy
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