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From |
"Martin Weiss" <martin.weiss1@gmx.de> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: 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 23:56:31 +0100 |

<> On loops you want to look at Nick`s http://www.stata-journal.com/sjpdf.html?articlenum=pr0005 Your id1 and id0 separation cries out for -separate- You will find listers reluctant to answer because of the attachment. Look at the FAQ, they are quite explicit... HTH Martin -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Stata Chris Sent: Freitag, 27. November 2009 23:49 To: statalist@hsphsun2.harvard.edu Subject: st: Constructing assignment var for Spatial RDD: For each id in region 1 need shortest distance to an id in region 0 Dear Statalisters, I would like to construct the assignment variable for a Spatial RDD, i.e. for each village in either of two regions I would like to know the distance to the border. Now, while I know the x- and y-coordinate of each village in the sample, I do not know the exact position of each point on the border; So my idea was to compute for each village in region 1 (0) the distance to each village in region 0 (1), as d=sqrt[ (y_1-y_0)^2 + (x_1-x_0)^2 ], and then take for each the minimum of these as the value for the assignment variable. Because both regions have quite a few villages, I will need to compute many such distances, so I think it will probably be best to do this with a loop. I have a rough idea of what the loop should do, but I'm not entirely sure how exactly to communicate this to Stata. I am attaching the dataset, and below I provide a rough indication of what I think are the necessary steps. If one of you was able to help me put this into a syntax Stata does actually understand, that would be awesome: gen id1 = id if treatment==1 gen id0 = id if treatment==0 for each id1 { for each id0 { gen dist_id1_id0 = sqrt( (zkx{id1}-zkx{id0})^2 + (zky{id1}-zky{id0})^2 ) gen assignmentvar_id1 = min (of all dist_id1_*) } } And then do the same also the other way round. Thank you so much, Chris * * 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/

**References**:**st: Constructing assignment var for Spatial RDD: For each id in region 1 need shortest distance to an id in region 0***From:*Stata Chris <statachris@gmail.com>

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