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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

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

Subject |
st: RE: RE: Data transformation |

Date |
Mon, 12 Nov 2007 12:29:13 -0000 |

I jumped to an incorrect reading of your problem through not reading it carefully enough. Point of curiosity: What about accidents involving three or more vehicles? Just not in the data? Point of technique: Keith's code was this bys Accidentnr: egen othersweight=sum(weight) bys Accidentnr: egen otherscost=sum(cost) replace othersweight=othersweight-weight replace otherscost=otherscost-cost rename weight ownweight rename cost owncost namely: other value = sum of two values - this value Given that there are two, and only two, cars for each accident, you can get there in this way too: bys Accidentnr : gen othersweight = weight[3 - _n] bys Accidentnr : gen otherscost = cost[3 - _n] The trick is simply a flip or reflection, exploiting the fact under -by:- the subscript _n is determined within groups. Thus if _n is 1, 3 - _n is 2, and vice versa. Actually, if there is just one car in any accident, a call to observation 3 - _n will yield missing values, which is appropriate too. Lina Jonsson I have a dataset concerning accidents involving two vehicles that I have in two formats, wide and long like this: long: Accidentnr vehiclenr weight cost 1 0 1000 35000 1 1 1500 150000 2 0 1200 150000 2 1 1700 750000 wide: Accidentnr weight0 weight1 cost0 cost1 1 1000 1500 35000 150000 2 1200 1700 150000 750000 Now I whould like to transform the data to a long format but with information also concering the other vehicle involved in each accident like this: Accidentnr vehiclenr ownweight othersweight owncost otherscost 1 0 1000 1500 35000 150000 1 1 1500 1000 150000 35000 2 0 1200 1700 150000 750000 2 1 1700 1200 750000 150000 * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**st: SV: RE: RE: Data transformation***From:*"Lina Jonsson" <lina.jonsson@vti.se>

**References**:**st: new package hangroot***From:*Maarten buis <maartenbuis@yahoo.co.uk>

**st: RE: new package hangroot***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

**st: Data transformation***From:*"Lina Jonsson" <lina.jonsson@vti.se>

**st: RE: Data transformation***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

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