Optimal Projections in the Distance-Based Statistical Methods

  • Chuanping Yu
  • Xiaoming HuoEmail author
Part of the Emerging Topics in Statistics and Biostatistics book series (ETSB)


This paper introduces a new way to calculate distance-based statistics, particularly when the data are multivariate. The main idea is to pre-calculate the optimal projection directions given the variable dimension, and to project multidimensional variables onto these pre-specified projection directions; by subsequently utilizing the fast algorithm that is developed in Huo and Székely (Technometrics, 58(4):435–447, 2016) for the univariate variables, the computational complexity can be improved from O(m2) to O(nm ⋅log(m)), where n is the number of projection directions and m is the sample size. When \(n \ll m/\log (m)\), computational savings can be achieved. The key challenge is how to find the optimal pre-specified projection directions. This can be obtained by minimizing the worse-case difference between the true distance and the approximated distance, which can be formulated as a nonconvex optimization problem in a general setting. In this paper, we show that the exact solution of the nonconvex optimization problem can be derived in two special cases: the dimension of the data is equal to either 2 or the number of projection directions. In the generic settings, we propose an algorithm to find approximate solutions. Simulations confirm the advantage of our method, in comparison with the pure Monte Carlo approach, in which the directions are randomly selected rather than pre-calculated.


Distance-based statistical methods Projection-based methods Quasi-Monte Carlo Statistical computing Random projections 



This project is partially supported by the Transdisciplinary Research Institute for Advancing Data Science (TRIAD),, which is a part of the TRIPODS program at NSF and locates at Georgia Tech, enabled by the NSF grant CCF-1740776. Both authors are also partially supported by the NSF grant DMS-1613152.


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© Springer Nature Switzerland AG 2020

Authors and Affiliations

  1. 1.School of Industrial and Systems EngineeringGeorgia Institute of TechnologyAtlantaUSA

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