--- On Fri, 3/7/09, Noori, Nazanin wrote:
> I want to run a spline cubic to assess the spline models
> with 95% CI reflecting mortality predictability of
> dietary phosphorus in a group.
>
> I have two variables:
>
> 1-Death
>
> 2- Phosphorus intake
>
> Would you please help me which syntax I should use? I want
> the Y axis to show the Log hazard ratio and the X axis to
> show the dietary phosphorus.
> Also I want to know if I want to adjust for age make second
> spline) what should I do. So far I ran these syntaxes:
>
>
> stset time to death, failure(death)
>
> stcox Phosphorus intake
>
> predict hr1, hr
>
> generate lnhr = ln(hr1)
The easiest way is to use restricted cubic splines because
these have already been implemented in official Stata's
-mkspline- command. Than use -adjust- to create adjusted
predictions and than plot these.
*------------- begin example ------------
sysuse cancer, clear
stset studytime, failure(died)
mkspline sp_age = age, cubic nknots(3)
xi: stcox i.drug sp_age*
adjust _Idrug_2=1 _Idrug_3=0, ///
by(age) ci replace xb
twoway rarea lb ub age || ///
line xb age, ///
legend(off) ///
ytitle("ln(hazard ratio)")
*------------- end example ------------
Hope this helps,
Maarten
-----------------------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
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