Statalist


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: st: Fractional Polynomials for Longitudinal Data


From   "Stas Kolenikov" <skolenik@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Fractional Polynomials for Longitudinal Data
Date   Mon, 29 Dec 2008 08:57:48 -0600

On 12/28/08, jasonm@ucla.edu <jasonm@ucla.edu> wrote:
> I'm new to fractional polynomial models. Is there a longitudinal data option
> for mfracpol or fracpoly?

In what particular way do you think of introducing a longitudinal
aspect to this procedure? To me, -*fracpol*- models are mostly useful
for smooth interpolation leading to prediction, and frankly I won't
see terribly much use for them in causal micro level inference --
that's what you are probably most interested in with longitudinal
data. If you are interested in flexible formulations with longitudinal
data, I'd probably be looking towards say B-splines, and/or their
multivariate generalizations. They allow for the familiar (X'X)X'y
formulae (or whatever you can have for more complex models) in
(generalized) linear models (something you can put into -xtm*- models
as predictors), at the same time producing smooth curves through data.

-- 
Stas Kolenikov, also found at http://stas.kolenikov.name
Small print: I use this email account for mailing lists only.
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index