I got some different results from S+ and an independent method (Statistica)
for the same data (10 uncensored failure times)
> survReg(Surv(ttf) ~ 1, data=data1, dist="weibull")
Call:
survReg(formula = Surv(ttf) ~ 1, data = data1, dist = "weibull")
Coefficients:
(Intercept)
5.200735
Scale= 0.1673101
Loglik(model)= -48.8 Loglik(intercept only)= -48.8
n= 10
whereas Statistica (2-p Weibull) gives scale = 181.4 and shape = 5.98
Now I am confused as to what parameterization is used in survReg().
Statistica uses exp(-(t/scale)^shape)) as Spencer suggests S+ does but the
results suggest survReg() uses something different but what?
Chris Wilkinson
-----Original Message-----
From: s-news-owner@lists.biostat.wustl.edu
[mailto:s-news-owner@lists.biostat.wustl.edu] On Behalf Of Terry Therneau
Sent: Sunday, May 16, 2004 9:13 PM
To: kamiltoth@yahoo.com
Cc: s-news@lists.biostat.wustl.edu
Subject: Re: [S] Weibull questions
2. How to fit a weibull?
Although survReg and censorreg were designed to allow for censored
data, they work just fine with ordinary Weibull data.
fit <- survReg(Surv(y) ~ x1 + x2 + ...., data=mydata,
dist='weibull')
Terry Therneau
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data1.txt
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