让时间序列反事实解释更真实,通过动态对齐优化生成合理时序结构。
Towards plausibility in time series counterfactual explanations
- 在输入空间直接梯度优化,结合软动态时间规整与目标类近邻增强真实性。
- 生成的反事实解释在有效性上表现良好,且与目标类分布对齐度显著提升。
- 适合关注时间序列可解释性、需保持真实时序模式的研究者使用。
我们提出一种生成时间序列分类问题中合理反事实解释的新方法。该方法在输入空间中进行基于梯度的优化,并引入软动态时间规整(soft-DTW)对齐与目标类的k-最近邻,有效促使生成的反事实具备真实的时序结构。整体优化目标为多方面损失函数,平衡有效性、稀疏性和接近性,并新增基于soft-DTW的可塑性组件。我们在多个维度上评估该方法与多种强基线方法的对比,结果表明:该方法在有效性上表现竞争,且在与目标类的分布对齐方面显著优于现有方法,体现更高的时序真实性。定性分析也揭示了现有方法在保持真实时序结构上的关键缺陷。本工作证明,所提方法能持续生成既有效又高度可信、符合时序规律的时间序列反事实解释。
原文摘要 · Abstract (English)
We present a new method for generating plausible counterfactual explanations for time series classification problems. The approach performs gradient-based optimization directly in the input space. To enforce plausibility, we integrate soft-DTW (dynamic time warping) alignment with $k$-nearest neighbors from the target class, which effectively encourages the generated counterfactuals to adopt a realistic temporal structure. The overall optimization objective is a multi-faceted loss function that balances key counterfactual properties. It incorporates losses for validity, sparsity, and proximity, alongside the novel soft-DTW-based plausibility component. We conduct an evaluation of our method against several strong reference approaches, measuring the key properties of the generated counterfactuals across multiple dimensions. The results demonstrate that our method achieves competitive performance in validity while significantly outperforming existing approaches in distributional alignment with the target class, indicating superior temporal realism. Furthermore, a qualitative analysis highlights the critical limitations of existing methods in preserving realistic temporal structure. This work shows that the proposed method consistently generates counterfactual explanations for time series classifiers that are not only valid but also highly plausible and consistent with temporal patterns.
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