Use qr.solve as default (instead of solve)
Drop collinear variables in pre_process_drdid.R (useful in drdid command but not other commands)
Add compatibility with R 3.5
Improve invertibility of outcome regression design matrix
Add new flags for non-unique unit identifier
Better handle of factor variables as 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).