Solving the minimum sum-of-squares clustering problem by hyperbolic smoothing and partition into boundary and gravitational regions

  • Authors:
  • Adilson Elias Xavier;Vinicius Layter Xavier

  • Affiliations:
  • Department of Systems Engineering and Computer Science, Graduate School of Engineering (COPPE), Federal University of Rio de Janeiro, P.O. Box 68511, Rio de Janeiro RJ 21941-972, Brazil;Department of Systems Engineering and Computer Science, Graduate School of Engineering (COPPE), Federal University of Rio de Janeiro, P.O. Box 68511, Rio de Janeiro RJ 21941-972, Brazil

  • Venue:
  • Pattern Recognition
  • Year:
  • 2011

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Abstract

This article considers the minimum sum-of-squares clustering (MSSC) problem. The mathematical modeling of this problem leads to a min-sum-min formulation which, in addition to its intrinsic bi-level nature, has the significant characteristic of being strongly nondifferentiable. To overcome these difficulties, the proposed resolution method, called hyperbolic smoothing, adopts a smoothing strategy using a special C^~ differentiable class function. The final solution is obtained by solving a sequence of low dimension differentiable unconstrained optimization subproblems which gradually approach the original problem. This paper introduces the method of partition of the set of observations into two nonoverlapping groups: ''data in frontier'' and ''data in gravitational regions''. The resulting combination of the two methodologies for the MSSC problem has interesting properties, which drastically simplify the computational tasks.