R
Alexander Begun and Felix Begun
Fits Parametric Gamma-Frailty Models with Non-Proportional Hazard Functions by maximum marginal likelihood. Provides parameter estimates, their standard errors and p-values, log-likelihood, concordance, contrasts (optional), and other characteristics (optional). Possible baseline hazards: Weibull, Gompertz.
The proportional hazard assumption is violated by using the second Cox-regression term multiplying the shape parameter. The first Cox-regression term is one used in the Cox proportional hazards model as hazard multiplier.
It is assumed that all subjects in a cluster share the same unobserved risk of failure (frailty) that is a gamma distributed random variable. The Weibull and the Gompertz baseline hazard functions are implemented.
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