Dalitz Plot Analyses of B^- \to D^+ \pi^-\pi^-, B^+ \to \pi^+ \pi^- \pi^+ and D^+_s \to \pi^+ \pi^- \pi^+ at BABAR

We report on the Dalitz plot analyses of B^- \to D^+ \pi^-\pi^-, B^+ \to \pi^+ \pi^- \pi^+ and D^+_s \to \pi^+ \pi^- \pi^+. The Dalitz plot method and the most recent BABAR results are discussed.