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st: Re: How to speed up loop


From   "Michael Blasnik" <michael.blasnik@verizon.net>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Re: How to speed up loop
Date   Wed, 15 Sep 2004 11:42:50 -0400

assuming 1 mother per household, how about no loop at all:

egen mage=max(age*(lineno==mlineno)), by(hhid)

This would result in a 0 for any household without a mother listed, which
you could easily change to missing or whatever you like.

Michael Blasnik
michael.blasnik@verizon.net

----- Original Message ----- 
From: "Friedrich Huebler" <huebler@rocketmail.com>
To: <statalist@hsphsun2.harvard.edu>
Sent: Wednesday, September 15, 2004 11:33 AM
Subject: st: How to speed up loop


> 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?
>
> Thank you,
>
> Friedrich Huebler
>
>
>
>
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