R help - Dec 2009 - Baseline survival estimate

Dear R-help,

I am trying to obtain the baseline survival estimate of a fitted Cox model
(S_0 (t)).  I know that previous posts have said use 'basehaz' but this
gives the baseline hazard function and not the baseline survival estimate.
Is there a way to obtain the baseline survival estimate or do I have to use
the formula which does something like S(t) = exp[- the integral from 0 to t
of h(u) du]?

Thank you for your assistance,

Laura

fit1 <-
coxph(Surv(tsecond/365,seccens)~stroke(smess1)+othnd(smess1)+relat(smess1)+asleep(smess1)+abeeg1(smess1)+treat(smess1),data=smess1)
basehaz(fit1)

where stroke is a function which creates a binary variable from the dataset
smess1 etc.

	[[alternative HTML version deleted]]

survival = exp(-hazard)

      -thomas

On Wed, 16 Dec 2009, Laura Bonnett wrote:
> Dear R-help,
>
> I am trying to obtain the baseline survival estimate of a fitted Cox model
> (S_0 (t)).  I know that previous posts have said use 'basehaz' but
this
> gives the baseline hazard function and not the baseline survival estimate.
> Is there a way to obtain the baseline survival estimate or do I have to use
> the formula which does something like S(t) = exp[- the integral from 0 to t
> of h(u) du]?
>
> Thank you for your assistance,
>
> Laura
>
> fit1 <-
>
coxph(Surv(tsecond/365,seccens)~stroke(smess1)+othnd(smess1)+relat(smess1)+asleep(smess1)+abeeg1(smess1)+treat(smess1),data=smess1)
> basehaz(fit1)
>
> where stroke is a function which creates a binary variable from the dataset
> smess1 etc.
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle