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
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