The copula echo state network

  • Authors:
  • Sotirios P. Chatzis;Yiannis Demiris

  • Affiliations:
  • Department of Electrical and Electronic Engineering, Imperial College London, United Kingdom;Department of Electrical and Electronic Engineering, Imperial College London, United Kingdom

  • Venue:
  • Pattern Recognition
  • Year:
  • 2012

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Abstract

Echo state networks (ESNs) constitute a novel approach to recurrent neural network (RNN) training, with an RNN (the reservoir) being generated randomly, and only a readout being trained using a simple, computationally efficient algorithm. ESNs have greatly facilitated the practical application of RNNs, outperforming classical approaches on a number of benchmark tasks. This paper studies the formulation of a class of copula-based semiparametric models for sequential data modeling, characterized by nonparametric marginal distributions modeled by postulating suitable echo state networks, and parametric copula functions that help capture all the scale-free temporal dependence of the modeled processes. We provide a simple algorithm for the data-driven estimation of the marginal distribution and the copula parameters of our model under the maximum-likelihood framework. We exhibit the merits of our approach by considering a number of applications; as we show, our method offers a significant enhancement in the dynamical data modeling capabilities of ESNs, without significant compromises in the algorithm's computational efficiency.