technically not response adaptive but keeps allocation ratio to control at the square root of active intervention arms
RAR.optimal(active)RAR.optimal returns a vector of probabilities with length of active.
the 'BATSS' ingredient 'active' corresponding to a logical vector of the same length and order as 'prob0' (i.e., number of arms initially included in the study including the reference group)) and indicating if each arm is active at the look of interest.