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From |
Rüdiger Vollmeier <ruediger.vollmeier@googlemail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: Matching procedure based on shortest distance given latitudes and longitudes |

Date |
Thu, 9 Feb 2012 11:34:41 +0100 |

Hello guys, I want to match observations in each observation in a given year with one observation in another year based on the shortest geographical distance between them given the latitudes and longitudes of each observation. I.e. the simplified structure of the dataset looks as follows: id year longitude latitude 1 2006 19.923 40.794 2 2006 19.949 40.711 1 2010 19.940 40.721 2 2010 22.001 50.122 Hence, I would like to match each observation in 2006 with the one observation in 2010 that is closest AND that had not been matched to any observation in 2006 before. The previously discussed -nearstat- command (thanks to Wilner!) cannot be applied directly to this problem as it could match the same observation in 2010 with multiple observations in 2006 (i.e. in this example, the year 2010 observation with id 1 is closest to both observations in 2006 - and hence would be matched). Does anybody have an idea for a nice solution or is there even a command out there that would match based on distance given the latitudes and longitudes? * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: Matching procedure based on shortest distance given latitudes and longitudes***From:*Robert Picard <picard@netbox.com>

**Re: st: Matching procedure based on shortest distance given latitudes and longitudes***From:*brendan.halpin@ul.ie (Brendan Halpin)

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