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From |
"Lina Jonsson" <lina.jonsson@vti.se> |

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

Subject |
st: SV: RE: RE: Data transformation |

Date |
Mon, 12 Nov 2007 17:22:17 +0100 |

Dear Nick For your curiosity I have arranged the data in a way that this subset only consists of two-vehicle accidents. Another question for my curiosity: Will your way of doing things take care of the problem of missing values that I face using Keiths code. Due to missing values I had to add a command after generating the "other"-variables, namely: replace othervar=. if othervar==var This only works when I have variables that never take the value zero, so not for dummies without further transformations. (Which I have done) The above command also makes the "other"-variable missing for cases where we actually have data on the "other"-variable but not on the "own"-variable, not a problem for me since I drop these observations anyway in the regression but it whould be nice to know how to solve this problem just for my curiosity. /Lina Jonsson > -----Ursprungligt meddelande----- > Från: owner-statalist@hsphsun2.harvard.edu > [mailto:owner-statalist@hsphsun2.harvard.edu] För Nick Cox > Skickat: den 12 november 2007 13:29 > Till: statalist@hsphsun2.harvard.edu > Ämne: st: RE: RE: Data transformation > > 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/ > * * 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: RE: SV: RE: RE: Data transformation***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

**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>

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

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