Re: [R] Weibull survival modeling with covariate

From: Göran Broström <gb_at_stat.umu.se>
Date: Thu 09 Jun 2005 - 16:01:09 EST

On Wed, Jun 08, 2005 at 08:39:21PM -0400, sms13+@pitt.edu wrote:
> I was wondering if someone familiar
> with survival analysis can help me with
> the following.
> I would like to fit a Weibull curve,
> that may be dependent on a covariate,
> my dataframe "labdata" that has the
> fields "cov", "time", and "censor". Do
> I do the following?
> wieb<-survreg(Surv(labdata$time,
> labadata$censor)~labdata$cov,
> dist="weibull")
>
> This returns:
> >weib
> Call:
> survreg(formula = Surv(labdata$time,
> labdata$censor) ~ labdata$cov,
> dist = "weibull")
>
> Coefficients:
> (Intercept) labdata$cov
> 8.091955112 0.001552897
>
> Scale= 0.7532474
>
> Loglik(model)= -12633.6
> Loglik(intercept only)= -12734.8
> Chisq= 202.41 on 1 degrees of
> freedom, p= 0
> n= 5496
>
>
> I am not quite sure how to use the
> output. I see that it gives the Scale
> parameter. How do I find the Shape
> paramater as a function of the
> covariate?

You don't. The analysis is performed on the logs of durations, so scale is transformed to location and shape to scale. For more intuitive output, use 'weibreg' in package 'eha'. It can also handle left truncated data. But only Weibull (and exponential) regression.  

>
> Thank you,
> Steven
>
> ---------------------------------------
> -------------------------
> Steven Shechter
> PhD Candidate in Industrial Engineering
> University of Pittsburgh
> www.pitt.edu/~sms13
>
> ______________________________________________
> 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
>

-- 
Göran Broström                    tel: +46 90 786 5223
Professor and Head
Department of Statistics          fax: +46 90 786 6614
Umeå University                   http://www.stat.umu.se/~goran.brostrom/
SE-90187 Umeå, Sweden             e-mail: gb@stat.umu.se

______________________________________________
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 Thu Jun 09 16:03:57 2005

This archive was generated by hypermail 2.1.8 : Fri 03 Mar 2006 - 03:32:27 EST