The goal of optrefine is to split existing strata (or none) into more refined strata that optimize covariate balance. Most often, propensity score strata are each split into two in order to achieve better covariate balance.

You can install the release version of optrefine from CRAN with:

install.packages("optrefine")

You can install the development version of optrefine from GitHub with:

# install.packages("devtools")
devtools::install_github("kkbrum/optrefine")