# st: RE: Re: How to speed up loop

 From "Nick Cox" To Subject st: RE: Re: How to speed up loop Date Wed, 15 Sep 2004 17:58:50 +0100

```Thanks for the compliment, but why the -if-?

If -mlineno- is missing, age[.] will be too,
and so the -if- is redundant.

Nick
n.j.cox@durham.ac.uk

> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of
> Ulrich Kohler
> Sent: 15 September 2004 17:48
> To: statalist@hsphsun2.harvard.edu
> Subject: st: Re: How to speed up loop
>
>
> Nick's approach is much better than mine. But probably with
> an if qualifier:
>
> . by hhid : gen mage = age[mlineno] if mlineno < .
>
> uli
>
> Nick Cox wrote:
> > Looks like
> >
> > by hhid : gen mage = age[mlineno]
> >
> > to me. No loops, no -merge-.
> >
> > Nick
> > n.j.cox@durham.ac.uk
> >
> > Friedrich Huebler
> >
> > > I appreciate the responses that I received so far but
> realize that my
> > > initial message was not precise enough.
> > >
> > > The variable mlineno lists the line number of a household member's
> > > mother. In household 1 in my example data, household
> member 2 is the
> > > mother of household member 3. In household 2, 1 is the
> mother of 2,
> > > and 3 is the mother of 4 and 5. I would like to create a variable
> > > that lists the age of each household member's mother. The result
> > > should look like this:
> > >
> > > hhid    lineno       age   mlineno      mage
> > >    1         1        32         .         .
> > >    1         2        30         .         .
> > >    1         3         5         2        30
> > >    2         1        68         .         .
> > >    2         2        41         1        68
> > >    2         3        40         .         .
> > >    2         4        17         3        40
> > >    2         5        14         3        40
> > >
> > > The loop that I am using to create the variable mage
> works perfectly
> > > but it is very slow with a large number of observations.
> > >
> > > Friedrich
> > >
> > > --- Friedrich Huebler <huebler@rocketmail.com> wrote:
> > > > I am looking for advice to speed up a loop. The loop determines
> > > > characteristics of other household members in household
> survey data
> > > > and is taken from this Stata FAQ:
> > > >
> > > > http://www.stata.com/support/faqs/data/members.html
> > > >
> > > > The data has the variables hhid (household ID), lineno
> (line number
> > > > of household member), age, and mlineno (mother's line number).
> > > >
> > > > hhid    lineno       age   mlineno
> > > >    1         1        32         .
> > > >    1         2        30         .
> > > >    1         3         5         2
> > > >    2         1        68         .
> > > >    2         2        41         1
> > > >    2         3        40         .
> > > >    2         4        17         3
> > > >    2         5        14         3
> > > >
> > > > The following code creates the variable mage with the
> mother's age.
> > > >
> > > > gen byte mage=.
> > > > sum lineno, meanonly
> > > > forvalues i = 1/`r(max)' {
> > > >   gen byte tag = 1 if lineno==`i'
> > > >   bysort hhid: egen byte iage = max(tag*age)
> > > >   replace mage=iage if mlineno==`i'
> > > >   drop tag iage
> > > >   }
> > > >
> > > > I tried changing -bysort hhid- to -by hhid- but the
> time needed for
> > > > the loop is the same. Running the loop -quietly- also makes no
> > > > difference. Can anything be done to make this loop go faster?
> >
> > *
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> > *   http://www.ats.ucla.edu/stat/stata/
>
> --
> kohler@wz-berlin.de
> +49 (030) 25491-361
>
>
> *
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>

*
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```