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Scalable Dictionary Classifiers for Time Series Classification

  • Matthew MiddlehurstEmail author
  • William Vickers
  • Anthony Bagnall
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 11871)

Abstract

Dictionary based classifiers are a family of algorithms for time series classification (TSC) that focus on capturing the frequency of pattern occurrences in a time series. The ensemble based Bag of Symbolic Fourier Approximation Symbols (BOSS) was found to be a top performing TSC algorithm in a recent evaluation, as well as the best performing dictionary based classifier. However, BOSS does not scale well. We evaluate changes to the way BOSS chooses classifiers for its ensemble, replacing its parameter search with random selection. This change allows for the easy implementation of contracting (setting a build time limit for the classifier) and check-pointing (saving progress during the classifiers build). We achieve a significant reduction in build time without a significant change in accuracy on average when compared to BOSS by creating a fixed size weighted ensemble selecting the best performers from a randomly chosen parameter set. Our experiments are conducted on datasets from the recently expanded UCR time series archive. We demonstrate the usability improvements to randomised BOSS with a case study using a large whale acoustics dataset for which BOSS proved infeasible.

Keywords

Time series Classification Dictionary Contracting 

Notes

Acknowledgements

This work is supported by the UK Engineering and Physical Sciences Research Council (EPSRC) iCASE award T206188 sponsored by British Telecom. The experiments were carried out on the High Performance Computing Cluster supported by the Research and Specialist Computing Support service at the University of East Anglia.

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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Matthew Middlehurst
    • 1
    Email author
  • William Vickers
    • 1
  • Anthony Bagnall
    • 1
  1. 1.School of Computing SciencesUniversity of East AngliaNorwichUK

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