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Re: st: RE: identify family members using -egen (group)


From   Amanda Fu <mandy.fu1@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: identify family members using -egen (group)
Date   Fri, 11 Nov 2011 22:11:28 -0500

Thank you for your kind help, Mr. Cox! The solution you give works
perfectly. I appreciate it.
Sincerely,
Amanda

On Fri, Nov 11, 2011 at 5:15 AM, Nick Cox <n.j.cox@durham.ac.uk> wrote:
> -egen, group()- cannot help you here without some prior work. The premise of -egen, group()- is that it groups observations with identical values on one or more variables. Your data do not satisfy that.
>
> You could apply -rowsort- first:
>
> . l
>
>     +-------------------------------------+
>     | id   fam~1_id   fam~2_id   fam~3_id |
>     |-------------------------------------|
>  1. |  1    missing    missing    missing |
>  2. |  2          3    missing    missing |
>  3. |  3          2    missing    missing |
>  4. |  4          5          6    missing |
>  5. |  5          4          6    missing |
>     |-------------------------------------|
>  6. |  6          4          5    missing |
>     +-------------------------------------+
>
> . rowsort id f*id , gen(s1-s4)
>
> . l
>
>     +------------------------------------------------------------------------+
>     | id   fam~1_id   fam~2_id   fam~3_id   s1        s2        s3        s4 |
>     |------------------------------------------------------------------------|
>  1. |  1    missing    missing    missing    1   missing   missing   missing |
>  2. |  2          3    missing    missing    2         3   missing   missing |
>  3. |  3          2    missing    missing    2         3   missing   missing |
>  4. |  4          5          6    missing    4         5         6   missing |
>  5. |  5          4          6    missing    4         5         6   missing |
>     |------------------------------------------------------------------------|
>  6. |  6          4          5    missing    4         5         6   missing |
>     +------------------------------------------------------------------------+
>
> . egen group = group(s*)
>
> . l
>
>     +--------------------------------------------------------------------------------+
>     | id   fam~1_id   fam~2_id   fam~3_id   s1        s2        s3        s4   group |
>     |--------------------------------------------------------------------------------|
>  1. |  1    missing    missing    missing    1   missing   missing   missing       1 |
>  2. |  2          3    missing    missing    2         3   missing   missing       2 |
>  3. |  3          2    missing    missing    2         3   missing   missing       2 |
>  4. |  4          5          6    missing    4         5         6   missing       3 |
>  5. |  5          4          6    missing    4         5         6   missing       3 |
>     |--------------------------------------------------------------------------------|
>  6. |  6          4          5    missing    4         5         6   missing       3 |
>     +--------------------------------------------------------------------------------+
>
>
> You must install -rowsort- first. -rowsort- is described in
>
> SJ-9-1  pr0046  . . . . . . . . . . . . . . . . . . .  Speaking Stata: Rowwise
>        (help rowsort, rowranks if installed) . . . . . . . . . . .  N. J. Cox
>        Q1/09   SJ 9(1):137--157
>        shows how to exploit functions, egen functions, and Mata
>        for working rowwise; rowsort and rowranks are introduced
>
> and may be downloaded from the Stata Journal files regardless of whether you subscribe to the Stata Journal. The article is apparently a good one anyway.
>
> Note that I copied your example as if you had strings, but -rowsort- works with numeric variables too.
>
> Nick
> n.j.cox@durham.ac.uk
>
> Amanda Fu
>
> I know there are discussions on how to identify siblings before on
> statalist. The solutions are using the same mother and fathor's ID.
> But I still have not figured out  how to identify family members in my
> data set, since there are no parents' ID.
>
> The data set looks like as follows:
> ---------------------------------------
> id       fam_member1_id    fam_member2_id   fam_member3_id
>
> 1            missing                   missing missing
> 2            3                             missing                     missing
> 3            2                             missing                     missing
> 4            5                              6     missing
> 5            4                              6     missing
> 6            4                              5     missing
> ............
> ----------------------------------
> That is, ID 2 and 3; 4,5, and 6 are in the same families.
> I tried to use
> . egen famid =group(id  fam_member1_id    fam_member2_id
> fam_member3_id),missing
> but the famid I got is not the same for a family.
> ----------------------------------the last column is what I want to get-----
> id       fam_member1_id    fam_member2_id   fam_member3_id     famid
>
> 1             missing                  missing
> missing            missing
> 2            3                             missing
> missing              1
> 3            2                             missing
> missing              1
> 4            5                              6
>    missing              2
> 5            4                              6
>    missing              2
> 6            4                              5
>    missing              2
> ............
> ----------------------------------
>
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