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arXiv 1602.05162math.STstat.TH
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M-完全和M-开集上叠加的Bayes解释

A Bayes interpretation of stacking for M-complete and M-open settings

Tri Le, Bertrand Clarke

摘要:

在没有真正的模型可以概念化的M-开放问题中,通常会从建模中退出,只寻求良好的预测。即使在M-完全问题中,采用预测方法也是非常有用的。堆叠是一种模型平均过程,它通过使用优化交叉验证标准的权重组合模型列表中的各个预测因子来给出复合预测因子。我们表明,堆叠权重也渐近最小化后验预期损失。因此,我们正式提供了交叉验证的贝叶斯理由。通常,权重被限制为正值并且总和为1。为了更大的一般性,我们省略了积极性约束,并放宽了“总和为一”的约束。一个关键问题是“平均值中应该有哪些预测因素?“我们首先验证堆叠误差仅取决于模型的跨度。然后,我们建议使用数据中的引导样本来生成可用于形成模型的经验基础元素。我们在两个计算示例中使用它来给出堆叠预测器,这些预测器是(i)数据驱动的,(ii)相对于组件预测器的数量最优,以及(iii)相对于每个预测器获得的权重最优。

英文摘要:

In M-open problems where no true model can be conceptualized, it is common to back off from modeling and merely seek good prediction. Even in M-complete problems, taking a predictive approach can be very useful. Stacking is a model averaging procedure that gives a composite predictor by combining individual predictors from a list of models using weights that optimize a cross-validation criterion. We show that the stacking weights also asymptotically minimize a posterior expected loss. Hence we formally provide a Bayesian justification for cross-validation. Often the weights are constrained to be positive and sum to one. For greater generality, we omit the positivity constraint and relax the `sum to one' constraint. A key question is `What predictors should be in the average?' We first verify that the stacking error depends only on the span of the models. Then we propose using bootstrap samples from the data to generate empirical basis elements that can be used to form models. We use this in two computed examples to give stacking predictors that are (i) data driven, (ii) optimal with respect to the number of component predictors, and (iii) optimal with respect to the weight each predictor gets.

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