The panels show the reachability plots resulting from clustering with different strategies of standardization. The points are color coded depending on the cluster they are member of. Vertical colored strips indicate the groups associated to the recovered open clusters. The relevant coefficients and scores are listed on top of each panel. Top panel: reachability plot obtained from clustering analysis in the [Fe/H]–[Si/H]–[Ni/H]–[Co/H]–[Ba/H] space without standardization. Second panel: reachability plot obtained from clustering analysis in the [Fe/H]–[Si/H]–[Ni/H]–[Co/H]–[Ba/H] space with standardization. Third panel: reachability plot obtained from clustering analysis in the [Fe/H]–[Si/Fe]–[Ni/Fe]–[Co/Fe]–[Ba/Fe] space without standardization. Bottom panel: reachability plot obtained from clustering analysis in the [Fe/H]–[Si/Fe]–[Ni/Fe]–[Co/Fe]–[Ba/Fe] space with standardization.