[R] error using frailty term

Terry Therneau
Sat, 03 Oct 2009 13:56:48 -0000

--- begin included message -----
T
rying to fit a model using the Surv() with a frailty term but get the
following cryptic error message:
------------------------------------------------------------------------------
Error in frailty.brent(sqrt(x), y, lower = 0) :
  Ties for max(y), I surrender
Calls: runplots ... coxpenal.fit -> eval -> eval -> <Anonymous>
-> frailty.brent
------------------------------------------------------------------------------
When I remove the frailty term from the model it runs just fine. Does
anyone know what this error message means?

Thanks,
M.

-------- end included message -----------

 What it means is that the function maximization routine "under the
covers" is
completely befuddled.  (I saw the "I give up" message fairly often in
the
earliest drafts of the code.)

  Solution: download the coxme package from CRAN -- superior in every way to
frailty() terms.  For one thing I made the maximizer much more intelligent: I
now use optim :-).

  	Terry Therneau