Updates theta as described by Nieto-Barajas (2003).
Cftheta(theta.s, lambda.r, times, delta, type.t, K, covar, m, s)1. Nieto-Barajas, L. E. & Walker, S. G. (2002). Markov beta and gamma processes for modelling hazard rates. Scandinavian Journal of Statistics 29, 413-424.
2. Nieto-Barajas, L. E. (2003). Discrete time Markov gamma processes and time dependent covariates in survival analysis. Bulletin of the International Statistical Institute 54th Session. Berlin. (CD-ROM)