A function to calculate outcomes for units in the period right before they become treated (this function can also be used to recover covariates, etc. in the period right before a unit becomes treated). For units that do not participate in the treatment (and therefore have group==0), they are assigned their outcome in the last period.
Arguments
- df
the data.frame used in the function
- idname
name of column that holds the unit id
- yname
name of column containing the outcome (or other variable) for which to calculate its outcome in the immediate pre-treatment period
- tname
name of column that holds the time period
- gname
name of column containing the unit's group