Degeneracy of the EM algorithm for the MLE of multivariate Gaussian mixtures and dynamic constraints

  • Authors:
  • Salvatore Ingrassia;Roberto Rocci

  • Affiliations:
  • Dipartimento Impresa, Culture e Societí, Universití di Catania, Corso Italia, 55-95129 Catania, Italy;Dipartimento SEFEMEQ, Universití di Roma "Tor Vergata", Roma, Italy

  • Venue:
  • Computational Statistics & Data Analysis
  • Year:
  • 2011

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Abstract

EM algorithms for multivariate normal mixture decomposition have been recently proposed in order to maximize the likelihood function in a constrained parameter space having no singularities and a reduced number of spurious local maxima. However, such approaches require some a priori information about the eigenvalues of the covariance matrices. The behavior of the EM algorithm near a degenerated solution is investigated. The obtained theoretical results would suggest a new kind of constraint based on the dissimilarity between two consecutive updates of the eigenvalues of each covariance matrix. The performances of such a ''dynamic'' constraint are evaluated on the grounds of some numerical experiments.