[R] frailty variance parameter in survreg()

[Jerome Asselin]

Is there a simple way to extract the frailty variance parameter (theta)?
Below is an example of the method that I have.

  library(survival)
  data(rats)
  rfit2b <- survreg(Surv(time, status) ~ rx +
                       frailty.gaussian(litter, df=13, sparse=TRUE), rats )

 {
  #According to rfit2b$printfun, this is the way to extract "theta"
  if (!is.null(rfit2b$history[[1]]$history))
   theta <- rfit2b$history[[1]]$history[nrow(rfit2b$history[[1]]$history), 1]
  else theta <- rfit2b$history[[1]]$theta
 }
  theta   # This is 0.01926811

#It would be a nice feature if the final variance estimate
#was directly accessible by:
  rfit2b$history[[1]]$theta   # This is 0.01926953   != theta 

Could we make it that way?

Sincerely,
Jerome Asselin

P.S.: I am using the survival package 2.9-6 on R 1.6.2 on RedHat Linux 7.2.

-- 

Jerome Asselin (Jérôme), Statistical Analyst
British Columbia Centre for Excellence in HIV/AIDS
St. Paul's Hospital, 608 - 1081 Burrard Street
Vancouver, British Columbia, CANADA V6Z 1Y6
Email: jerome at hivnet.ubc.ca
Phone: 604 806-9112   Fax: 604 806-9044