$$X_{{\mathrm{P.}}_1那{\mathrm{P.}}_2那\mathrm{......}那{\mathrm{P.}}_N}={\displaystyle \underset{j_1=1}{\overset{m_1}{\sigma .}}\frac{1}{m_1}{\mathrm{\omega .}}_{m_1}^{{\mathrm{P.}}_1{j}_1}{\displaystyle \underset{j_2=1}{\overset{m_2}{\sigma .}}\frac{1}{m_2}{\mathrm{\omega .}}_{m_2}^{{\mathrm{P.}}_2{j}_2}\mathrm{......}{\displaystyle \underset{j_N=1}{\overset{m_N}{\sigma .}}\frac{1}{m_N}{\mathrm{\omega .}}_{m_N}^{{\mathrm{P.}}_N{j}_N}}}}{y}_{j_1那j_2那\mathrm{......}那j_N}。$$