Matching incomplete time series with dynamic time warping: an algorithm and an application to post-stroke rehabilitation

  • Authors:

  • Paolo Tormene;Toni Giorgino;Silvana Quaglini;Mario Stefanelli

  • Affiliations:

  • Laboratory for Biomedical Informatics, Computer Engineering and Systems Science, Universití di Pavia, Via Ferrata 1, I-27100 Pavia, Italy;Laboratory for Biomedical Informatics, Computer Engineering and Systems Science, Universití di Pavia, Via Ferrata 1, I-27100 Pavia, Italy;Laboratory for Biomedical Informatics, Computer Engineering and Systems Science, Universití di Pavia, Via Ferrata 1, I-27100 Pavia, Italy;Laboratory for Biomedical Informatics, Computer Engineering and Systems Science, Universití di Pavia, Via Ferrata 1, I-27100 Pavia, Italy

  • Venue:
  • Artificial Intelligence in Medicine
  • Year:
  • 2009

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Abstract

Objective: The purpose of this study was to assess the performance of a real-time (''open-end'') version of the dynamic time warping (DTW) algorithm for the recognition of motor exercises. Given a possibly incomplete input stream of data and a reference time series, the open-end DTW algorithm computes both the size of the prefix of reference which is best matched by the input, and the dissimilarity between the matched portions. The algorithm was used to provide real-time feedback to neurological patients undergoing motor rehabilitation. Methods and materials: We acquired a dataset of multivariate time series from a sensorized long-sleeve shirt which contains 29 strain sensors distributed on the upper limb. Seven typical rehabilitation exercises were recorded in several variations, both correctly and incorrectly executed, and at various speeds, totaling a data set of 840 time series. Nearest-neighbour classifiers were built according to the outputs of open-end DTW alignments and their global counterparts on exercise pairs. The classifiers were also tested on well-known public datasets from heterogeneous domains. Results: Nonparametric tests show that (1) on full time series the two algorithms achieve the same classification accuracy (p-value =0.32); (2) on partial time series, classifiers based on open-end DTW have a far higher accuracy (@k=0.898 versus @k=0.447;p