用时空卷积建模时间序列协方差,提升动态数据处理稳定性。
Spatiotemporal Covariance Neural Networks
- 基于样本协方差矩阵,设计联合时空卷积的关联学习模型
- 在线更新下仍稳定,比在线时间PCA更抗扰动
- 适合流式、非平稳时间序列,尤其对变化数据适应性强
多变量时间序列的时空交互建模至关重要却具挑战性,因其结构不规则且未知。数据的统计特性可提供有用先验,现有方法常依赖相关性或协方差网络及主成分分析(PCA)流程。然而,当特征值接近时,PCA及其时序扩展在协方差特征向量上易出现不稳定,难以应用于动态和流式数据场景。为此,本文借鉴PCA与图卷积滤波器的类比关系,提出时空协方差神经网络(STVNN),该模型在时间序列样本协方差矩阵上运行,利用联合时空卷积建模数据。为应对流式与非平稳环境,引入参数与协方差矩阵的在线更新机制,并证明其对在线估计不确定性具有鲁棒性,优于基于时间PCA的方法。实验验证了理论结果,表明STVNN在多变量时间序列处理中具备竞争力,能适应数据分布变化,且稳定性比在线时间PCA高一个数量级以上。
原文摘要 · Abstract (English)
Modeling spatiotemporal interactions in multivariate time series is key to their effective processing, but challenging because of their irregular and often unknown structure. Statistical properties of the data provide useful biases to model interdependencies and are leveraged by correlation and covariance-based networks as well as by processing pipelines relying on principal component analysis (PCA). However, PCA and its temporal extensions suffer instabilities in the covariance eigenvectors when the corresponding eigenvalues are close to each other, making their application to dynamic and streaming data settings challenging. To address these issues, we exploit the analogy between PCA and graph convolutional filters to introduce the SpatioTemporal coVariance Neural Network (STVNN), a relational learning model that operates on the sample covariance matrix of the time series and leverages joint spatiotemporal convolutions to model the data. To account for the streaming and non-stationary setting, we consider an online update of the parameters and sample covariance matrix. We prove the STVNN is stable to the uncertainties introduced by these online estimations, thus improving over temporal PCA-based methods. Experimental results corroborate our theoretical findings and show that STVNN is competitive for multivariate time series processing, it adapts to changes in the data distribution, and it is orders of magnitude more stable than online temporal PCA.
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