arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1707.05232math.STstat.APstat.TH
收藏

关于Lasso改装策略

On Lasso refitting strategies

Evgenii Chzhen, Mohamed Hebiri, Joseph Salmon

摘要:

l_1-惩罚估计量的一个众所周知的缺点是大系数向零的系统收缩。一个简单的补救方法是将Lasso视为一个模型选择程序,并在选定的支持上执行第二个改装步骤。在这项工作中,我们正式的改装的概念,并提供Oracle边界任意改装程序的拉索解决方案。基于最小二乘的估计量修正技术是目前应用最广泛的估计量修正技术之一,但由于修正后的估计量的符号可能与原估计量的符号相反,因此存在可解释性问题。这个问题源于这样一个事实,即最小二乘重构只考虑Lasso解的支持,避免任何关于符号或振幅的信息。为此,我们定义了一个符号一致的改装作为一个任意改装过程,保持第一步Lasso解决方案的迹象,并提供Oracle不等式,这样的估计。最后,我们考虑特殊的改装策略:Bregman Lasso和Boosted Lasso。Bregman Lasso有一个富有成效的特性,可以收敛到符号最小二乘重新拟合(带符号约束的最小二乘),这提供了更好的可解释性。我们还研究了Bregman Lasso改装的正交设计的情况下,所提出的方法背后提供简单的直观。相比之下,Boosted Lasso考虑了第一个Lasso步骤的大小信息,并允许开发更好的预测预言率。最后,我们进行了广泛的数值研究,以显示在不同的合成和半真实的情况下,一种方法比其他方法的优势。

英文摘要:

A well-know drawback of l_1-penalized estimators is the systematic shrinkage of the large coefficients towards zero. A simple remedy is to treat Lasso as a model-selection procedure and to perform a second refitting step on the selected support. In this work we formalize the notion of refitting and provide oracle bounds for arbitrary refitting procedures of the Lasso solution. One of the most widely used refitting techniques which is based on Least-Squares may bring a problem of interpretability, since the signs of the refitted estimator might be flipped with respect to the original estimator. This problem arises from the fact that the Least-Squares refitting considers only the support of the Lasso solution, avoiding any information about signs or amplitudes. To this end we define a sign consistent refitting as an arbitrary refitting procedure, preserving the signs of the first step Lasso solution and provide Oracle inequalities for such estimators. Finally, we consider special refitting strategies: Bregman Lasso and Boosted Lasso. Bregman Lasso has a fruitful property to converge to the Sign-Least-Squares refitting (Least-Squares with sign constraints), which provides with greater interpretability. We additionally study the Bregman Lasso refitting in the case of orthogonal design, providing with simple intuition behind the proposed method. Boosted Lasso, in contrast, considers information about magnitudes of the first Lasso step and allows to develop better oracle rates for prediction. Finally, we conduct an extensive numerical study to show advantages of one approach over others in different synthetic and semi-real scenarios.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑