We present preliminary results on the measurement of the I=1/2 \(K \pi\) \(\mathcal{S}\)-wave through a model independent partial wave analysis of \(\eta_c\) decays to \(K^0_S K^+ \pi^-\) and \(K^+ K^- \pi^0\) produced in two-photon interactions. We also perform a Dalitz plot analysis of the \(J/\psi\) decays to \(\pi^+ \pi^- \pi^0\) and \(K^+ K^- \pi^0\) produced by the initial state radiation process.