论文标题
在多项式时间内计算时间序列的连续动态时间扭曲
Computing Continuous Dynamic Time Warping of Time Series in Polynomial Time
论文作者
论文摘要
动态时间扭曲可以说是时间序列最流行的相似性度量,我们将时间序列定义为一维多边形曲线。动态时间扭曲的缺点是它对时间序列的采样率很敏感。 Fréchet距离是一种越来越受欢迎的替代方案,但是它的缺点是它对离群值敏感。 连续动态时间扭曲(CDTW)是最近提出的替代方案,没有表现出上述缺点。 CDTW结合了Fréchet距离的连续性与动态时间扭曲的总和,从而产生了相似的度量,这对采样速率和离群值都有牢固。在Brankovic等人最近的实验性工作中,证明在CDTW下的聚类避免了在动态时间扭曲和FRéchet距离下聚类时出现的有害伪影。尽管具有优势,但CDTW的主要缺点是,在多项式时间或其他情况下,没有确切的计算CDTW算法。 在这项工作中,我们介绍了第一个用于计算一维曲线CDTW的精确算法。我们的算法在时间$ o(n^5)$中用于一对一维曲线,每个曲线最多都有$ n $。在我们的算法中,我们在CDTW的动态程序中传播连续函数,其中主要困难在于界定功能的复杂性。我们认为,我们的结果是CDTW成为曲线之间的实际相似性度量的重要第一步。
Dynamic Time Warping is arguably the most popular similarity measure for time series, where we define a time series to be a one-dimensional polygonal curve. The drawback of Dynamic Time Warping is that it is sensitive to the sampling rate of the time series. The Fréchet distance is an alternative that has gained popularity, however, its drawback is that it is sensitive to outliers. Continuous Dynamic Time Warping (CDTW) is a recently proposed alternative that does not exhibit the aforementioned drawbacks. CDTW combines the continuous nature of the Fréchet distance with the summation of Dynamic Time Warping, resulting in a similarity measure that is robust to sampling rate and to outliers. In a recent experimental work of Brankovic et al., it was demonstrated that clustering under CDTW avoids the unwanted artifacts that appear when clustering under Dynamic Time Warping and under the Fréchet distance. Despite its advantages, the major shortcoming of CDTW is that there is no exact algorithm for computing CDTW, in polynomial time or otherwise. In this work, we present the first exact algorithm for computing CDTW of one-dimensional curves. Our algorithm runs in time $O(n^5)$ for a pair of one-dimensional curves, each with complexity at most $n$. In our algorithm, we propagate continuous functions in the dynamic program for CDTW, where the main difficulty lies in bounding the complexity of the functions. We believe that our result is an important first step towards CDTW becoming a practical similarity measure between curves.