R help - Mar 2009 - survreg help in R

Hey all,
I am trying to use the survreg function in R to estimate the mean and
standard deviation to come up with the MLE of alpha and lambda for the
weibull distribution.  I am doing the following:
times<-c(10,13,18,19,23,30,36,38,54,56,59,75,93,97,104,107,107,107)
censor<-c(1,0,0,1,0,1,1,0,0,0,1,1,1,1,0,1,0,0)
survreg(Surv(times,censor),dist='weibull')
and I get the following error:
> survreg(Surv(times,censor),dist='weibull')
Error in x$terms : $ operator is invalid for atomic vectors

I am fairly new to R and don't understand what I am doing wrong.  Any help
would be great.
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I think R and survival took a look at what you provided for a formula  
to survreg and rejected it because it had no lh-rh separator, "~", and
thus no rh terms. Turns out that it also expects a dataframe even if  
both terms for the Surv function are already given and there is  
nothing further to be evaluated. Try adding:
 > dft <- data.frame(times=times, censor=censor)
 > survreg(Surv(times,censor) ~ , dist='weibull', data=dft)
Error: syntax error
 > survreg(Surv(times,censor) ~ ., dist='weibull', data=dft)
Call:
survreg(formula = Surv(times, censor) ~ ., data = dft, dist =
"weibull")

Coefficients:
(Intercept)
    4.591518

Scale= 0.5965153

Loglik(model)= -50.4   Loglik(intercept only)= -50.4
n= 18

-- 


On Mar 8, 2009, at 1:34 PM, murphy82nd wrote:
>
> Hey all,
> I am trying to use the survreg function in R to estimate the mean and
> standard deviation to come up with the MLE of alpha and lambda for the
> weibull distribution.  I am doing the following:
> times<-c(10,13,18,19,23,30,36,38,54,56,59,75,93,97,104,107,107,107)
> censor<-c(1,0,0,1,0,1,1,0,0,0,1,1,1,1,0,1,0,0)
> survreg(Surv(times,censor),dist='weibull')
> and I get the following error:
>> survreg(Surv(times,censor),dist='weibull')
> Error in x$terms : $ operator is invalid for atomic vectors
>
> I am fairly new to R and don't understand what I am doing wrong.   
> Any help
> would be great.
> -- 
> View this message in context:
http://www.nabble.com/survreg-help-in-R-tp22400405p22400405.html
> Sent from the R help mailing list archive at Nabble.com.
>
David Winsemius, MD
Heritage Laboratories
West Hartford, CT

> survreg(Surv(times,censor),dist='weibull')
Error in x$terms : $ operator is invalid for atomic vectors

 You need a right-hand side for the formula
 	survreg(Surv(times, censor) ~1, dist='weibull')
 	
 In your code the first argument was not recognized as a "formula",
and the
program subsequently got very confused.  The error message was not very helpful,
unfortunately.  
 
  FYI: from an updated help page for survreg.distributions
  
> y<-rweibull(1000, shape=2, scale=5)
> survreg(Surv(y)~1, dist="weibull")
Coefficients:
(Intercept) 
   1.607516 

Scale= 0.5187037 

 Survreg parameters are scale=1/shape, intercept=log(scale).  This is because 
the Weibull has been imbedded in a general location-scale framework.

	Terry Therneau