[R] survreg with frailty

[Terry Therneau]

  The combination of survreg + gamma frailty = invalid model, i.e., the example
that you quote.
  
  I did not realize that this had been added to the survreg help file until very 
recently.  I will try to fix the oversight.  Other, more detailed documentation 
states that Gaussian frailty + AIC is the only valid random effects choice for 
survreg.  
  
  Details: frailty(x) with no optional arguments defaults to "mle" as the method 
of choosing the variance of the random effect, via a calculation that is 
specific to the Cox model.  
  
  	Terry Therneau