Exact mean computation in dynamic time warping spaces

Averaging time series under dynamic time warping is an important tool for improving nearest-neighbor classifiers and formulating centroid-based clustering. The most promising approach poses time series averaging as the problem of minimizing a Fréchet function. Minimizing the Fréchet function is NP-h...

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Vydáno v:Data mining and knowledge discovery Ročník 33; číslo 1; s. 252 - 291
Hlavní autoři: Brill, Markus, Fluschnik, Till, Froese, Vincent, Jain, Brijnesh, Niedermeier, Rolf, Schultz, David
Médium: Journal Article
Jazyk:angličtina
Vydáno: New York Springer US 01.01.2019
Springer Nature B.V
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ISSN:1384-5810, 1573-756X
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Shrnutí:Averaging time series under dynamic time warping is an important tool for improving nearest-neighbor classifiers and formulating centroid-based clustering. The most promising approach poses time series averaging as the problem of minimizing a Fréchet function. Minimizing the Fréchet function is NP-hard and so far solved by several heuristics and inexact strategies. Our contributions are as follows: we first discuss some inaccuracies in the literature on exact mean computation in dynamic time warping spaces. Then we propose an exponential-time dynamic program for computing a global minimum of the Fréchet function. The proposed algorithm is useful for benchmarking and evaluating known heuristics. In addition, we present an exact polynomial-time algorithm for the special case of binary time series. Based on the proposed exponential-time dynamic program, we empirically study properties like uniqueness and length of a mean, which are of interest for devising better heuristics. Experimental evaluations indicate substantial deficits of state-of-the-art heuristics in terms of their output quality.
Bibliografie:ObjectType-Article-1
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ISSN:1384-5810
1573-756X
DOI:10.1007/s10618-018-0604-8