[R] Parametric survival models with left truncated, right censored data

[Terry Therneau]

 Bill Meeker's programs for reliability analysis can fit this, they are part of 
his SPLIDA package for Splus.  I'm not sure that anyone has ported these to R 
however.
 
 The survreg routine does not handle this case, and psm call survreg to do the 
actual work.
 
 	Terry Therneau