针对高维重尾局部平稳时间序列,提出稀疏学习新框架并证明预测误差收敛性。
Sparsified-Learning for High-Dimensional Heavy-Tailed Locally Stationary Time Series, Concentration and Oracle Inequalities
- 结合加法模型与核平滑,设计稀疏惩罚估计方法
- 在重尾噪声下实现慢速与快速收敛的预测误差界
- 适合处理高维、非平稳、长尾数据的统计学习场景
稀疏学习广泛应用于各类机器学习任务,通过添加正则项约束模型参数结构。本文针对高维重尾局部平稳时间序列(LSTS)构建灵活的稀疏学习框架。数据生成机制包含随时间平滑变化的回归函数,观测噪声服从子威布尔和规则变化分布。提出一种融合加法建模与核平滑的稀疏诱导估计方法,并定义加法核平滑假设类。在局部平稳动态下,假设β-混合系数指数衰减,推导出带有核权重的局部平稳过程在重尾噪声下的集中不等式。进一步建立非渐近预测误差界,在不同稀疏结构(包括Lasso与总变差惩罚)下获得慢速与快速收敛率,基于最小二乘损失。数值实验在模拟的LSTS上进行,采用子威布尔与帕累托噪声,验证尾部行为对预测误差的影响,分析样本量增大时不同协变量维度下的表现。
原文摘要 · Abstract (English)
Sparse learning is ubiquitous in many machine learning tasks. It aims to regularize the goodness-of-fit objective by adding a penalty term to encode structural constraints on the model parameters. In this paper, we develop a flexible sparse learning framework tailored to high-dimensional heavy-tailed locally stationary time series (LSTS). The data-generating mechanism incorporates a regression function that changes smoothly over time and is observed under noise belonging to the class of sub-Weibull and regularly varying distributions. We introduce a sparsity-inducing penalized estimation procedure that combines additive modeling with kernel smoothing and define an additive kernel-smoothing hypothesis class. In the presence of locally stationary dynamics, we assume exponentially decaying $β$-mixing coefficients to derive concentration inequalities for kernel-weighted sums of locally stationary processes with heavy-tailed noise. We further establish nonasymptotic prediction-error bounds, yielding both slow and fast convergence rates under different sparsity structures, including Lasso and total variation penalization with the least-squares loss. To support our theoretical results, we conduct numerical experiments on simulated LSTS with sub-Weibull and Pareto noise, highlighting how tail behavior affects prediction error across different covariate-dimensions as the sample size increases.
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