a 2x2 subset of original data.
This is the subset with post treatment periods separately for the
treated group and comparison group and pre-treatment periods in the period
immediately before the treated group became treated."><meta property="og:description" content="A function for computing a 2x2 subset of original data.
This is the subset with post treatment periods separately for the
treated group and comparison group and pre-treatment periods in the period
immediately before the treated group became trea