accepts formula object and data, creates the data used for refinement
parse_and_prep(formula, data)
data.frame object with the data prepared for refinement. Data will have unit, time, treatment columns in that order, followed by everything else.
formula object specifying how to construct the data used for refinement. This is likely to be some variation of the covs.formula argument.
data.frame object to be used to create the data needed for refinement. data has unit, time, treatment columns in that order, followed by everything else