[R] rpart with interval censored data crashes R

[Terry Therneau]

 Thank you for the input on rpart -- I just saw the message today.
 
 1. You are right, it should not crash.  Why it crashes rpart is simply that I 
(the author) never ever tried using interval censored data in the call.  Real 
users try the most amazing things....
  I'll fix it in my local version, but putting in a "no no no" message.  My 
local version and the R version, maintained by Brian, have drifted quite far 
apart however.
  
  2. Rpart deals with right censored data using the same trick as Cox models, by 
thinking of it as observation of a Poisson process; number of events seen over a 
given time window.  The fact that the number is always 0 or 1 doesn't hinder the 
mathematical trick, which is based in counting process theory.
  BUT - the trick only works for right censored data.
  
  Using the mid points of your intervals is the only approach that comes readily 
to mind.
  
  	Terry Therneau