针对时间序列对比学习中的错误负样本问题,提出新框架提升表示质量。
StatioCL: Contrastive Learning for Time Series via Non-Stationary and Temporal Contrast
- 基于非平稳性和时间依赖性设计对比样本,避免误判相似性。
- 在真实数据集上召回率提升2.9%,错误负样本减少19.2%。
- 特别适合标签稀缺或数据量小的场景,表现更鲁棒。
对比学习(CL)在时间序列表示学习中展现出巨大潜力,通过将相似样本嵌入靠近而将不相似样本拉远。然而,现有方法常因忽视时间序列固有特性,随机选取不同片段作为负样本,导致引入错误负样本(FNPs),进而造成表示学习偏差、性能下降和效率低下。本文首次系统定义并分类时间序列中的错误负样本:语义错误负样本(源于忽略标签类别间的相似性,与非平稳性相关)和时间错误负样本(源于忽视时间邻近性)。为此,我们提出StatioCL,一种新型对比学习框架,通过捕捉非平稳性与时间依赖性,有效缓解两类错误负样本并修正学习到的表示。通过解析和区分非平稳状态(反映趋势或动态与数据模式的相关性),StatioCL准确捕获语义特征,消除语义错误负样本;同时基于时间依赖性建立细粒度相似度层级,捕捉片段间的时间邻近差异,缓解时间错误负样本。在多个真实世界基准时间序列分类数据集上评估,StatioCL显著优于当前最优对比学习方法,召回率提升2.9%,错误负样本减少19.2%。更重要的是,该方法在数据效率和标签稀缺情况下的鲁棒性也明显增强。
原文摘要 · Abstract (English)
Contrastive learning (CL) has emerged as a promising approach for representation learning in time series data by embedding similar pairs closely while distancing dissimilar ones. However, existing CL methods often introduce false negative pairs (FNPs) by neglecting inherent characteristics and then randomly selecting distinct segments as dissimilar pairs, leading to erroneous representation learning, reduced model performance, and overall inefficiency. To address these issues, we systematically define and categorize FNPs in time series into semantic false negative pairs and temporal false negative pairs for the first time: the former arising from overlooking similarities in label categories, which correlates with similarities in non-stationarity and the latter from neglecting temporal proximity. Moreover, we introduce StatioCL, a novel CL framework that captures non-stationarity and temporal dependency to mitigate both FNPs and rectify the inaccuracies in learned representations. By interpreting and differentiating non-stationary states, which reflect the correlation between trends or temporal dynamics with underlying data patterns, StatioCL effectively captures the semantic characteristics and eliminates semantic FNPs. Simultaneously, StatioCL establishes fine-grained similarity levels based on temporal dependencies to capture varying temporal proximity between segments and to mitigate temporal FNPs. Evaluated on real-world benchmark time series classification datasets, StatioCL demonstrates a substantial improvement over state-of-the-art CL methods, achieving a 2.9% increase in Recall and a 19.2% reduction in FNPs. Most importantly, StatioCL also shows enhanced data efficiency and robustness against label scarcity.
Thank you to arXiv for use of its open access interoperability. PaperDance 不是 arXiv 官方产品;中文卡片由大模型生成,请以原文为准。