Hi, I am wondering if there is a package for doing conditional logistic 
regression for nested case-control study as described in "Estimation of absolute 
risk from nested case-control data" by Langholz and Borgan (1997) where 
Horvitz-Thompson sampling weight (log of (number in the risk set divided by the 
number sampled)) is used with regression. In SAS Proc Phreg, this is implemented 
as an offset (offset=logweight). I checked clogistic() in Epi package and 
clogit() in survival package, but couldn't figure out how to incorporate this 
weighting with either. 


Also when considering nested case-control sampling for Cox proportional hazards 
model, the above method can estimate absolute risk of developing disease over a 
specified time interval. Appreciate if anyone has any suggestion on how to do 
this in R.

Thanks very much!

John


      
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