[R] change the reference level in plot(summary(cph-fit))

[David Winsemius]

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.

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David Winsemius
Alameda, CA, USA