segmentation.OU.specialCase.same_shifts
keeps the same shifts position,
and optimize the sum of costs using function
best_scenario
segmentation.OU.specialCase.same_shifts(phylo, shifts_old, D, Xp, ...)
List containing : beta_0 : the optimal value at the root shifts : list containing the computed tau and delta costs : vector of costs
a phylogenetic tree
the previous list of shifts (only position is used)
This is the best move if keeping the previous shifts positions.