Thank you.
--- Alan Riley <[email protected]> wrote:
> Ricardo Ovaldia ([email protected]) wonders if Mata
> will help him
> solve the following problem:
> > I have household data with one observation per
> family
> > member. All House hold have one or both parents
> and
> > anywhere from 1 to seven children. All households
> have
> > children but no grandparents or other relatives.
> Here
> > are a few tipical observations and relevant
> variables:
> >
> > . cl familyid subjid relation
> >
> > familyid subjid relation
> > 1. 1001 1 f
> > 2. 1001 2 m
> > 3. 1001 3 c
> > 4. 1001 4 c
> > 5. 1002 1 m
> > 6. 1002 2 c
> > 7. 1002 3 c
> > 8. 1003 1 m
> > 9. 1003 2 f
> > 10. 1003 3 c
> >
> > where for -relation-: f=father, m=mother and
> c=child
> >
> > I want to create two new variables which hold, for
> the
> > children, their parent's -subjectid- as follows:
> >
> > familyid subjid relation fatherid
> motherid
> > 1. 1001 1 f .
> .
> > 2. 1001 2 m .
> .
> > 3. 1001 3 c 1
> 2
> > 4. 1001 4 c 1
> 2
> > 5. 1002 1 m .
> .
> > 6. 1002 2 c .
> 2
> > 7. 1002 3 c .
> 2
> > 8. 1003 1 m .
> .
> > 9. 1003 2 f .
> .
> > 10. 1003 3 c 2
> 1
> >
> > I wrote a program to do this but is very slow
> because
> > it loops over observations.
> > I think that if I recode this using -mata- it
> would be
> > faster, but I not sure where to begin. Any
> assistance
> > or suggestions will be greatly appreciated.
>
> Ricardo is correct that if he rewrites his loop in
> Mata, it
> will be faster. However, this is still not the
> optimal solution.
> Mata is useful for many data management tasks, such
> as reading
> and manipulating files and performing left-hand-side
> indexing (i.e.
> when you want to achieve something like
>
> . generate y[somevar] = x
>
> which isn't possible in Stata but is possible using
> Mata and matrix views
> onto the Stata dataset in Mata).
>
> However, Ricardo can achieve his results with just a
> few Stata commands
> and creative sorting:
>
>
> generate fatherid = subjid if relation=="f"
> sort familyid fatherid
> by familyid: replace fatherid = fatherid[1] if
> relation=="c"
> replace fatherid = . if relation != "c"
>
> generate motherid = subjid if relation=="m"
> sort familyid motherid
> by familyid: replace motherid = motherid[1] if
> relation=="c"
> replace motherid = . if relation != "c"
>
> sort familyid subjid
> list
>
> Note that the last -list- shows different values for
> motherid
> in observations 6 and 7 from what Ricardo showed in
> his example.
> However, I believe that motherid should be '1' in
> those two
> observations as produced by the code above.
>
>
> Alan
> ([email protected])
> *
> * 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/
>
Ricardo Ovaldia, MS
Statistician
Oklahoma City, OK
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*
* 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/
