coxph() and intervening events

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch 
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Vegard Andersen
Sent: Thursday, January 13, 2005 12:52 PM
To: r-help at stat.math.ethz.ch
Subject: [R] coxph() and intervening events


Hello!

I am using the coxph() function for counting process data. I want to  
include an intervening event as one of my covariates. In 
order to do this  
I have split the relevant observations in my data at the time of  
intervention. But I have not found any way to "inform" 
coxph() of the id  
of these observations. The result of this is that coxph() 
interprets the  
split data as extra observations, which is wrong.
Do anyone have a suggestion on how to specify the ID of subjects  
experiencing intervening events?
Or maybe other solutions on how to perform a cox regression 
including an  
intervening event covariate?

Thanks in advance!

-- 
Best regards,
Vegard Andersen
Institute of Community Medicine
University of Tromso
Tromso, Norway

vegard.andersen at ism.uit.no