arXiv:2509.03649cs.AI2025-09

研究如何分割时间序列以提升SHAP解释质量,发现等长分段更优。

An Empirical Evaluation of Factors Affecting SHAP Explanation of Time Series Classification

  • 用8种分段算法对时间序列进行分组,降低SHAP计算开销。
  • 分段数量比分段方法对解释质量影响更大,等长分段表现最佳。
  • 提出按分段长度加权的归一化方法,显著提升解释可靠性。

可解释人工智能(XAI)在理解复杂时间序列分类(TSC)模型预测方面日益重要。其中,SHapley Additive exPlanations(SHAP)虽被广泛认为是优秀归因方法,但其计算复杂度随特征数呈指数增长,限制了其在长时序数据上的应用。为此,近期研究通过分段聚合特征,为连续时间点组计算单一归因值,大幅降低运行时间。然而最优分段策略仍不明确。本文系统评估了8种时间序列分段算法,分析分段结构对解释质量的影响。采用InterpretTime和AUC Difference两种标准XAI评估方法,在多变量(MTS)与单变量(UTS)时间序列上进行实验。结果表明,分段数量对解释质量的影响大于分段方法本身。等长分段始终优于多数自定义分段算法。此外,本文提出一种新颖的归因归一化技术,按分段长度加权,显著提升解释质量。

原文摘要 · Abstract (English)

Explainable AI (XAI) has become an increasingly important topic for understanding and attributing the predictions made by complex Time Series Classification (TSC) models. Among attribution methods, SHapley Additive exPlanations (SHAP) is widely regarded as an excellent attribution method; but its computational complexity, which scales exponentially with the number of features, limits its practicality for long time series. To address this, recent studies have shown that aggregating features via segmentation, to compute a single attribution value for a group of consecutive time points, drastically reduces SHAP running time. However, the choice of the optimal segmentation strategy remains an open question. In this work, we investigated eight different Time Series Segmentation algorithms to understand how segment compositions affect the explanation quality. We evaluate these approaches using two established XAI evaluation methodologies: InterpretTime and AUC Difference. Through experiments on both Multivariate (MTS) and Univariate Time Series (UTS), we find that the number of segments has a greater impact on explanation quality than the specific segmentation method. Notably, equal-length segmentation consistently outperforms most of the custom time series segmentation algorithms. Furthermore, we introduce a novel attribution normalisation technique that weights segments by their length and we show that it consistently improves attribution quality.

可解释AI时间序列SHAP分段优化

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