Re: st: any idea?

[Nick Cox <njcoxstata@gmail.com>]

In addition to Red's helpful suggestions, note that technique for such
paired data was discussed in

http://www.stata-journal.com/sjpdf.html?articlenum=dm0043

which is publicly accessible. The problem is that the identifiers in
Rodrigo's example appear to make little sense. How is Stata expected
to know that 1 and 4, 2 and 5, 3 and 6 are paired? Perhaps the
structure of the dataset is clearer in practice. If so, basic
calculations are just a couple of lines or so.

Nick
njcoxstata@gmail.com


On 14 December 2013 15:33, Red Owl <rh.redowl@liu.edu> wrote:
> Rodrigo,
>
> The following code demonstrates an approach with basic loops.
> It could be made more efficient with a different loop
> structure, but this approach may be more informative.
>
> *** BEGIN CODE ***
> * Build demo data set.
> clear
> * Length is capitalized to distinguish from length().
> input id str5(side) Length
> 1 right 10
> 2 right 15
> 3 right 11
> 4 left  13
> 5 left  10
> 6 left  12
> end
>
> gen byte newvar1 = .
> forval i = 1/3 {
>   replace newvar1 = Length[`i'] - Length[4] in `i'
>   }
> forval i = 4/6 {
>   replace newvar1 = Length[`i'] - Length[1] in `i'
>   }
>
> gen byte newvar2 = .
> forval i = 1/3 {
>   replace newvar2 = Length[`i'] - Length[5] in `i'
>   }
> forval i = 4/6 {
>   replace newvar2 = Length[`i'] - Length[2] in `i'
>   }
>
> gen byte newvar3 = .
> forval i = 1/3 {
>   replace newvar3 = Length[`i'] - Length[6] in `i'
>   }
> forval i = 4/6 {
>   replace newvar3 = Length[`i'] - Length[3] in `i'
>   }
>
> list, noobs sep(0)
> *** END CODE ***
>
> Good luck.
>
> Red Owl
> redowl@liu.edu
>
>
>> Y.R.E. Retamal" <yrer2@cam.ac.uk> Sat, 14 Dec 2013 12:08:42:
>>
>> Dear list
>>
>> I am very complicated trying to perform an analysis using STATA and I
> cannot find the way. Maybe you could help me. I want to create some new
> variables containing the difference between the length of two
> individuals from different groups:
>>
>>
>> id     side     length      newvar1       newvar2      newvar3
>> 1      right      x           x-j           x-k          x-l
>> 2      right      y           y-j           y-k          y-l
>> 3      right      z           z-j           z-k          z-l
>> 4      left       j           j-x           j-y          j-z
>> 5      left       k           k-x           k-y          k-z
>> 6      left       l           l-x           l-y          l-z
>>
>>
>> I do not know if I do explain myself clearly, the individuals are
> bones (clavicles, for example), so it is possible that some right
> clavicles pair-match with left clavicles, following the idea that an
> individual has bone of similar length.
>>
>> Any help could bring me a light!
>> Best wishes
>>
>> Rodrigo
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