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st: Modelling Relative Risks with -fracpoly-

From   Colin Angus <>
Subject   st: Modelling Relative Risks with -fracpoly-
Date   Wed, 20 Mar 2013 14:52:34 +0000

Hi Statalist,

I'm using the -fracpoly- command to model the log relative risk of an
event as a function of a single continuous exposure variable, where
the reference category for my relative risk is those with an exposure
of 0 (i.e. my log RR at 0 exposure is 0). So my command is:

-fracpoly: regress logRR exposure [weight=weight]-

I cannot see how to force the fitted fractional polynomial function
through the origin. Even if I use the -nocon- command to supress the
constant term, the transformations of the exposure variable mean that
the fitted value at 0 isn't 0.

Can anybody help me?


Colin Angus
Research Assistant
Health Economics and Decision Science

School of Health and Related Research (ScHARR)
University of Sheffield
Regent's Court
30 Regent Street
S1 4DA
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