On Thu, 13 Jan 2005, Vegard Andersen wrote:
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.
No, it is not wrong.
Do anyone have a suggestion on how to specify the ID of subjects experiencing intervening events?
You can specify the ID by including cluster(id) in your formula. This gives you a model-robust sandwich variance. You don't need to do this and it is not standard (though IMO it's a good idea).
-thomas
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