Is it possible there is a typo in your attached code? You wrote... loglik <- function(theta, param) { sum(d1*log(hazard1(x1, param)) - chazard1(x1,param) + d2*log(hazard2(x2, theta, param)) - chazard2(x2, theta, param)) } / 10000 Confidentiality Notice: This e-mail message, including any a...{{dropped}}