Re: [R] median survival time from survfit

From: Dunia Scheid <dunia.scheid_at_gmail.com>
Date: Fri, 18 Mar 2011 16:33:42 +0000

Many thanks!

2011/3/18 Marc Schwartz <marc_schwartz_at_me.com>

> On Mar 18, 2011, at 6:06 AM, Dunia Scheid wrote:
>
> > Hello,
> >
> > I am trying to compute the mdeian of the survival time from the function
> > survfit:
> >
> >> fit <- survfit(Surv(time, status) ~ 1)
> >> fit
> > Call: survfit(formula = Surv(time, status) ~ 1)
> >
> > records n.max n.start events median 0.95LCL 0.95UCL
> > 111 111 111 20 NA NA NA
> >
> > The results is NA? the fit$surv gives values between 1 and 0.749! Am I
> doing
> > this correct? Is there a correct way to do this?
> >
> > Many thanks for your help,
> > Dunia
>
>
> Median survival is the time at which the survivorship function equals 0.5.
> Since your minimum value appears to be 0.749, you never get there, thus the
> output shows NA.
>
> If you did not have any censored observations, median survival would also
> be the point at which 50% of your sample has not yet observed the event of
> interest.
>
> See ?print.survfit for additional information specific to this function.
>
> HTH,
>
> Marc Schwartz
>
>

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