Sharp quadratic majorization in one dimension

  • Authors:
  • Jan de Leeuw;Kenneth Lange

  • Affiliations:
  • Department of Statistics, University of California, Los Angeles, CA 90095, United States;Department of Biomathematics, University of California, Los Angeles, CA 90095, United States and Department of Human Genetics, University of California, Los Angeles, CA 90095, United States and De ...

  • Venue:
  • Computational Statistics & Data Analysis
  • Year:
  • 2009

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Abstract

Majorization methods solve minimization problems by replacing a complicated problem by a sequence of simpler problems. Solving the sequence of simple optimization problems guarantees convergence to a solution of the complicated original problem. Convergence is guaranteed by requiring that the approximating functions majorize the original function at the current solution. The leading examples of majorization are the EM algorithm and the SMACOF algorithm used in Multidimensional Scaling. The simplest possible majorizing subproblems are quadratic, because minimizing a quadratic is easy to do. In this paper quadratic majorizations for real-valued functions of a real variable are analyzed, and the concept of sharp majorization is introduced and studied. Applications to logit, probit, and robust loss functions are discussed.