From: Valentin Dimitrov <vsdimitrov_at_yahoo.com>

Date: Sat 08 Jul 2006 - 10:45:57 EST

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sat Jul 08 10:51:52 2006

Date: Sat 08 Jul 2006 - 10:45:57 EST

*>
*

> Those are not proportional hazards families of

*> distributions. That is, if
**> the distribution is gaussian for one value of the
**> hazard ratio parameters
**> it will not be gaussian for any other value.
**>
**> You can get accelerated failure models with these
**> distributions using
**> survreg() in the survival package.
**>
**>
**> -thomas
*

I do not need a accelerated failure model, but a
proportional hazard model with a f0= weibull,
exponential, loglogistic or lognormal baseline
distribution. The hazard function is

lambda(t)=exp(Xi*beta)*lambda0(t),

where lambda0 is the baseline hazard

lambda0(t)=f0(t)/(1-F0(t)) where f0 and F0 are the
baseline density and cumulative distribution
functions.

This is a proportional hazard model since the ratio
lambda(t|Xi)/lambda(t|Xj)=exp(Xi*beta)/exp(Xj*beta)
does not depend on t.

Valentin

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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sat Jul 08 10:51:52 2006

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