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Re: st: Why does mkspline only have "restricted" cubic splines and what does it mean in practice?


From   Maarten buis <[email protected]>
To   [email protected]
Subject   Re: st: Why does mkspline only have "restricted" cubic splines and what does it mean in practice?
Date   Tue, 8 Mar 2011 13:07:23 +0000 (GMT)

--- On Tue, 8/3/11, Nick Cox wrote:
> I am really surprised that you feel you need so many knots,
> even if you have ages that aren't integers in your data.

In general I agree with Nick (naturally), but there are 
exceptions. For example, I have modeled how the probability
of giving birth depends on age, cohort and education, and
I ended up needing quite a lot of knots to get a reasonable 
representation of the effect of age, which as you can imagine
has a very specific curvilinear effect. 

-- Maarten

--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany

http://www.maartenbuis.nl
--------------------------


      

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