R help - Jan 2014 - change the reference level in plot(summary(cph-fit))

I have use the plot(summary(cph-fit)) to plot the hazard ratio plot.
*Can I change the reference level in the plot, for example, use [1999,
2002) as the reference level?*

*Thanks*

*Yao Zhu*


*Department of Urology Fudan University Shanghai Cancer CenterShanghai,
China*

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On Jan 4, 2014, at 8:37 PM, zhu yao wrote:
> I have use the plot(summary(cph-fit)) to plot the hazard ratio plot.
> *Can I change the reference level in the plot, for example, use [1999,
> 2002) as the reference level?*
I do not think we have enough information to be sure what you mean, but I would
remind you that Cox models are always estimations of the relative risk for
differences in covariates. If the era for which 1999-2002 is one instance as a
covariate (rather than as the time variable), then you could certainly construct
differences from that era.

--

David Winsemius
Alameda, CA, USA