Improve code to avoid redundant data checks

Use fastglm instead of parglm for improved speed

Restore solve as default to invert matrix, as it is faster than qr.solve for small matrices.

Improve error handling for non-invertible matrices.

Changing estimation methods for fastglm and parglm (in place of lm and glm).

Do not let the estimated propensity score be above 1 - 1e-6 (instead of 1 - e-16).

Speed up data processing using Rcpp

The weights are now enforced to be normalized and have mean 1 across all observations.

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

- Fixed links

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 Santâ€™Anna and Zhao (2020).