R help - Oct 2008 - Fitting weibull and exponential distributions to left censoring data

Dear R-users
I have some datasets, all left-censoring, and I would like to fit
distributions to (weibull,exponential, etc..). I read one solution using the
function survreg in the survival package. i.e
survreg(Surv(...)~1, dist="weibull") but it returns only the scale
parameter.

Does anyone know how to successfully fit the exponential, weibull etc...
distributions to left-censoring data?

Thanks
Borja

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Dear Barja

Have you looked at "gamlss" y "gamlss.dist" libaries?

There some functions called WEI, WEI2, and WEI3

Cheers,

Fer

Use the survreg function.
 
 There are many different ways to parameterize a Weibull.  The survreg function 
imbeds it a general location-scale familiy, which is a different 
parameterization than the rweibull function. 
 
> y <- rweibull(1000, shape=2, scale=5)
> survreg(Surv(y)~1, dist="weibull")
Coefficients:
(Intercept) 
   1.592543 

Scale= 0.5096278 

Loglik(model)= -2201.9   Loglik(intercept only)= -2201.9

----

 survreg's scale  =    1/(rweibull shape)
 survreg's intercept = log(rweibull scale)
 For the log-likelihood all parameterizations lead to the same value.

  There is not "right" or "wrong" parameterization for a
Weibull (IMHO), but
there certainly is a lot of room for confusion.  This comes up enough that I 
have just added it as an example in the survreg help page, which will migrate to
the general R distribution in due course.
  
  Terry Therneau