st: Modelling Relative Risks with -fracpoly-

[Colin Angus <c.r.angus@sheffield.ac.uk>]

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?

Thanks,

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
Sheffield
S1 4DA
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