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Re: st: calculate pairwise distance between tracts


From   sara borelli <[email protected]>
To   [email protected]
Subject   Re: st: calculate pairwise distance between tracts
Date   Fri, 5 Nov 2010 19:52:52 +0000 (GMT)

Hi Nichols,
thank you very much for you reply,
that was really helpful
sara
--- Gio 4/11/10, Austin Nichols <[email protected]> ha scritto:

> Da: Austin Nichols <[email protected]>
> Oggetto: Re: st: calculate pairwise distance between tracts
> A: [email protected]
> Data: Giovedì 4 novembre 2010, 22:34
> sara borelli <[email protected]>
> :
> If you really want to cross the data, see -help cross-, but
> that may
> produce a really large dataset.
> You should consider looping over observations and computing
> the
> distance of each tract from tract i within the loop,
> computing what
> you need and saving only the relevant info. See also e.g.
> http://www.stata.com/statalist/archive/2009-07/msg00257.html
> FYI, -vincenty- is on SSC.
> 
> On Thu, Nov 4, 2010 at 5:21 PM, sara borelli <[email protected]>
> wrote:
> > Dear statalister
> > I am trying to calcluate pariwise distance between
> census tracts whithin state. I have longitude and latitude
> for each tract and I know vincenty command calculate
> distance
> > However, I am having sme troubles to organize data in
> the appropriate way to apply the command
> >
> > suppose I have
> > tract
> > 1
> > 2
> > 3
> >
> > if I put the data in the form
> >
> > tract_orgin     tract_Dest   long_orig  
>  long_dest  lat_orig    lat_dest
> > 1               1
> > 1               2
> > 1               3
> > 2               1
> > 2               2
> > 2               3
> > 3               1
> > 3               2
> > 3               3
> >
> >  if I organize the data in this way I can apply
> > vincety (lat_orig long_orig lat_dest long_dest) whihc
> gives me distance between any 2 tracts
> >
> > the problem is that I am having hard time to organize
> the data in that format given the large number of census
> tracts
> >
> > any suggestion on how to do this efficiently?
> > thanks
> >
> 
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