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Re: st: Terminating a loop when a certain value is reached.


From   Stephen Cranney <scranney@sas.upenn.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Terminating a loop when a certain value is reached.
Date   Wed, 3 Apr 2013 07:45:05 -0400

Thank you Maarten. I think that, because some demographic events are
by their nature sequential (e.g. post-partum infertility always needs
to follow a birth so that the mother isn't pregnant twice in two
months), that for certain probablistic microsimulations there's no way
around looping over observations. However, for most of my simulation
purposes, the slides you present are quite helpful  (and eminently
comprehensible).

Thanks again,

Stephen

On Tue, Apr 2, 2013 at 4:31 AM, Maarten Buis <maartenlbuis@gmail.com> wrote:
> On Mon, Apr 1, 2013 at 8:26 PM, Stephen Cranney wrote:
>> Basically, I'm
>> trying to make a microsimulation program in Stata because the other
>> microsimulation programs are very technical and require sophisticated
>> programming knowledge if you want to customize them to suit your
>> needs, whereas a microsimulation program in Stata would be much more
>> accessible and customizable. Hence my interest in keeping the code in
>> Stata, even though alternative coding languages would be more
>> efficient overall.
>
> Loops in such simulations in Stata are often unnecessary. Not only are
> the unnecessary, they often make your code more complex than it needs
> to be and are thus a source of error (as you have noticed).  The magic
> commands/prefixes for avoiding such loops in Stata are -by- and
> -expand-. If the purpose of this excercise is to make use of the
> simplicity of the Stata language, then you really need to make heavy
> use of these commands to avoid loops. Here is a presentation on how to
> create such demographic micro simulations without looping in Stata.
>
> <http://www.maartenbuis.nl/presentations/konstanz11.pdf>
>
> Hope this helps,
> Maarten
>
> ---------------------------------
> Maarten L. Buis
> WZB
> Reichpietschufer 50
> 10785 Berlin
> Germany
>
> http://www.maartenbuis.nl
> ---------------------------------
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-- 
Stephen Cranney

PhD Candidate
Graduate Group in Demography
University of Pennsylvania
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