提出变量变换下损失函数一致性的理论框架,统一理解实际应用中的变换机制。
Variable transformations in consistent loss functions
- 系统分析仅对观测值或联合预测与观测进行双射变换的场景
- 证明变换后损失仍保持一致性的充要条件,拓展了奥思班德原理
- 可用于构建新可识别、可引出的统计量,如g-变换期望和g-变换分位数
在严格一致损失函数中使用变量变换的现象普遍存在,但缺乏理论基础。本文建立了一个理论框架,形式化刻画此类变换损失函数的一致性性质。分析聚焦于两类情形:(a) 仅对实现变量施加变换;(b) 对预测与实现变量同时施加双射变换。这两类情形扩展了奥思班德揭示原理所确立的仅对预测变量变换的框架。我们进一步推导出(严格)识别函数的相应刻画。该理论框架广泛适用于统计与机器学习方法。例如,我们将框架应用于Bregman损失和期望损失函数,解释了使用变换损失训练模型的实证发现,并系统构造出新的可识别与可引出函数,分别称为g-变换期望和g-变换期望值。在模拟数据与真实数据上的应用展示了其在多种场景下的实用性。通过融合理论洞察与实践应用,本工作推进了复杂预测任务中损失函数设计的严谨方法。
原文摘要 · Abstract (English)
The empirical use of variable transformations within (strictly) consistent loss functions is widespread, yet a theoretical understanding is lacking. To address this gap, we develop a theoretical framework that establishes formal characterizations of (strict) consistency for such transformed loss functions. Our analysis focuses on two interrelated cases: (a) transformations applied solely to the realization variable and (b) bijective transformations applied jointly to both the realization and prediction variables. These cases extend the well-established framework of transformations applied exclusively to the prediction variable, as formalized by Osband's revelation principle. We further develop analogous characterizations for (strict) identification functions. The resulting theoretical framework is broadly applicable to statistical and machine learning methodologies. For instance, we apply the framework to Bregman and expectile loss functions to interpret empirical findings from models trained with transformed loss functions and systematically construct new identifiable and elicitable functionals, which we term respectively $g$-transformed expectation and $g$-transformed expectile. Applications of the framework to simulated and real-world data illustrate its practical utility in diverse settings. By unifying theoretical insights with practical applications, this work advances principled methodologies for designing loss functions in complex predictive tasks.
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