Provide log-likelihood function for exponential distribution with cured population
loglik_Chen_exponential(par, df)The negative value of the log-likelihood function given parameter
par and the dataset df
a vector with two elements, where the first element denotes the logistic of the proportion of the cured population, and the second element denotes the log of the hazard rate.
The subject-level event data, including time
and event.
Chen, Tai-Tsang. "Predicting analysis times in randomized clinical trials with cancer immunotherapy." BMC medical research methodology 16.1 (2016): 1-10.