• drop collinear variables in pre_process_drdid.R (useful in drdid command but not other commands)

• Add compatibility with R 3.5

• Ensure the idname is always provided (regardless of panel data or repeated cross section data setup)

• Add new flags for non-unique unit identifier

• Better handle of factor variables as covariates

• Fix issue with NA in covariates
• Allows for treating covariates as factor and alike when computing DiD

• Improve error and warning handling due to collinearity and convergence issues.

• First official version of package, functions for computing a variety of difference-in-differences (DiD) estimators for the ATT.

• Documentation is improved compared to the devel version, including examples for every function now.

• Created wrapper function drdid, ordid and ipwdid to implement doubly-robust, outcome regression and inverse probability weighted DID estimators.

• Add dataset used in the empirical application of Sant’Anna and Zhao (2020).