Thanks Nick,
A variation on "levelsof id if <condition>" appears to accomplish what I need.
It is far more efficient with respect to programmer time and effort but I haven't checked whether it is cpu-cycle efficient.
Tom
Thomas J. Steichen
[email protected]
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Facts do not cease to exist because they are ignored. - Aldous Huxley
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> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Nick Cox
> Sent: Friday, July 22, 2005 3:03 PM
> To: [email protected]
> Subject: st: RE: How to capture record info where "something"
> about the record is true?
>
>
> -findobs- by Sean Becketti is the most substantial
> work in this area that springs to mind.
>
> I can't suggest anything much simpler than
>
> gen long id = _n
>
> su id if <condition>, meanonly
>
> list id if <condition>
>
> levelsof id if <condition>
>
> Nick
> [email protected]
>
> Steichen, Thomas J.
>
> > I need to efficiently capture, for example, the record id
> > where something is true about that record.
> >
> > For example, if I have the following made-up data:
> >
> > id x
> >
> > a 6
> > b 32
> > c 6
> > d 11
> >
> > I may want to capture a record id where x = max(x).
> > I know I can get it via:
> >
> > . egen mx = max(x)
> > . gen rx = 1 if x == mx
> > . sort rx
> > . local id_info = id (or, more accurately, id[1])
> > . di "ID info: `id_info'"
> > ID info: b
> >
> > But an egen, gen, and sort seems to be an expensive way to do
> > this with a large dataset.
> >
> > The above solution will, of course, only capture one record
> > id, where x=max(x).
> >
> > If I had wanted x=min(x), it would be nice if id_info
> > contained "a c". This is doable also, but becomes even more
> > expensive in
> > computing time.
> >
> > Can someone propose a more efficient way or point out a
> > built-in command that I've missed?
>
> *
> * 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/
>
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