rstanarm is an R package that emulates other R model-fitting functions but uses Stan (via the rstan package) for the back-end estimation. The primary target audience is people who would be open to Bayesian inference if using Bayesian software were easier but would use frequentist software otherwise.
If you are new to rstanarm we recommend starting with the tutorial vignettes.
Install the latest release from CRAN
Instructions for installing the latest development version from GitHub can be found in the rstanarm Readme.
If you are interested in contributing to the development of rstanarm please see the Developer notes.