## Overview

hesim is a modular and computationally efficient R package for health economic simulation modeling and decision analysis that provides a general framework for integrating statistical analyses with economic evaluation. The package supports cohort discrete time state transition models (DTSTMs), N-state partitioned survival models (PSMs), and individual-level continuous time state transition models (CTSTMs), encompassing both Markov (time-homogeneous and time-inhomogeneous) and semi-Markov processes. It heavily utilizes Rcpp and data.table, making individual-patient simulation, probabilistic sensitivity analysis (PSA), and incorporation of patient heterogeneity fast.

Features of the current version can be summarized as follows:

• Cohort DTSTMs, N-state PSMs, and individual-level CTSTMs that encompass Markov and semi-Markov processes
• Options to build models via mathematical expressions using nonstandard evaluation or directly from fitted statistical models
• Parameter estimates from either an R based model or from an external source
• Convenience functions for sampling model parameters from parametric distributions or via bootstrapping
• Parameter uncertainty propagated with PSA
• Modeling patient heterogeneity
• Performing cost-effectiveness analyses and representing decision uncertainty from PSAs
• Simulation code written in C++ to boost performance

## Installation

You can install the current release from CRAN or the most up to date development version from GitHub.

# Install from CRAN:
install.packages("hesim")

# Install the development version from GitHub:
# install.packages("devtools")
devtools::install_github("hesim-dev/hesim")