Health Economic Simulation Modeling and Decision Analysis R package hesim version 0.5.8 A modular and computationally efficient R package for parameterizing, simulating, and analyzing health economic simulation models. The package supports cohort discrete time state transition models (Briggs et al. 1998) <doi:10.2165/00019053-199813040-00003>, N-state partitioned survival models (Glasziou et al. 1990) <doi:10.1002/sim.4780091106>, and individual-level continuous time state transition models (Siebert et al. 2012) <doi:10.1016/j.jval.2012.06.014>, encompassing both Markov (time-homogeneous and time-inhomogeneous) and semi-Markov processes. Decision uncertainty from a cost-effectiveness analysis is quantified with standard graphical and tabular summaries of a probabilistic sensitivity analysis (Claxton et al. 2005, Barton et al. 2008) <doi:10.1002/hec.985>, <doi:10.1111/j.1524-4733.2008.00358.x>. Use of C++ and data.table make individual-patient simulation, probabilistic sensitivity analysis, and incorporation of patient heterogeneity fast. Software Depends: R (>= 3.5.0) Imports: data.table, flexsurv, ggplot2, MASS, msm, Rcpp (>= 0.12.16), R6, stats, survival LinkingTo: Rcpp, RcppArmadillo Suggests: covr, kableExtra, knitr, magrittr, mstate, nnet, numDeriv, pracma, rmarkdown, scales, testthat, truncnorm Devin Incerti <devin.incerti@gmail.com> Comprehensive R Archive Network (CRAN) Devin Incerti [aut, cre], Jeroen P. Jansen [aut], Mark Clements [aut], R Core Team [ctb] (hesim uses some slightly modified C functions from base R) GPL-3 2026-01-13 application/tgz https://CRAN.R-project.org/package=hesim doi:10.32614/CRAN.package.hesim