search for: censorind

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2009 Jun 24
1
Coxph frailty model counting process error X matrix deemed singular
Hello, I am currently trying to simulate data and analyze it using the frailty option in the coxph function. I am working with recurrent event data, using counting process notation. Occasionally, (about 1 in every 100 simulations) I get the following warning: Error in coxph(Surv(start, end, censorind) ~ binary + uniform + frailty(subject, : X matrix deemed to be singular; variable 2 My data is structured as follows: I have a Bernoulli random variable (parameter=0.5) (labeled "binary") and a second variable which was generated as seq(0.02, 1, 0.02), which is labeled as "unifo...