R help - Mar 2009 - AFT model

Hi,
  In the package survival, using the function survreg for AFT model, I 
only see 4 distributions for the response y:  weibull, gaussian, 
logistic, lognormal and log-logistic, which correspond to certain 
distributions for the error terms. I'm wondering if there is a package 
or how to obtain the parameter estimates (the beta's are of great 
interest) from the AFT model (maximizing log-likelihood with censored 
data as in Klein and Moeschberger book) if we have
1) error ~ Cauchy(0,1)
2) error comes from a contaminated gaussian dist., for example,
density of error, f(x) = 0.9*phi(x, mean=0, sd=1) + 0.1*phi(x, mean=0, 
sd=3), where phi(.) is the standard gaussian pdf.


Thank you,

T.N.

On Tue, 17 Mar 2009, tsn4867 wrote:
>    Hi,
> In the package survival, using the function survreg for AFT model, I only
see
> 4 distributions for the response y:  weibull, gaussian, logistic, lognormal
and
> log-logistic, which correspond to certain distributions for the error
terms.
> I'm wondering if there is a package or how to obtain the parameter
estimates
> (the beta's are of great interest) from the AFT model (maximizing 
> log-likelihood with censored data as in Klein and Moeschberger book) if we
have
> 1) error ~ Cauchy(0,1)
> 2) error comes from a contaminated gaussian dist., for example,
> density of error, f(x) = 0.9*phi(x, mean=0, sd=1) + 0.1*phi(x, mean=0,
sd=3),
> where phi(.) is the standard gaussian pdf.
If you look at
    ?survreg.distributions
it has an example showing how to specify your own distributions.

      -thomas

Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle