Sufficient dimension reduction for classification using
     principal optimal transport direction

       Cheng Meng1 Jun Yu2 Jingyi Zhang3 Ping Ma4 Wenxuan Zhong4
      1
       Institute of Statistics and Big Data, Renmin University of China
       2
      School of Mathematics and Statistics, Beijing Institute of Technology
          3
           Center for Statistical Science, Tsinghua University
           4
            Department of Statistics, University of Georgia
                   C ...