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arXiv 1408.2156math.STcs.LGstat.MLstat.TH
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EM算法的统计保证:从总体到基于样本的分析

Statistical guarantees for the EM algorithm: From population to sample-based analysis

University of California, Berkeley(加州大学伯克利分校)

Sivaraman Balakrishnan, Martin J. Wainwright, Bin Yu

摘要:

我们开发了一个通用框架,证明严格保证EM算法的性能和称为梯度EM的变体。我们的分析分为两个部分:治疗这些算法在人口水平(在无限数据的限制),其次是结果,适用于更新的基础上的一个有限集的样本。首先,我们描述了人口的任何全球最大化的可能性的吸引区域。这种表征是基于一种新的观点的EM更新作为扰动形式的可能性上升,或在平行的梯度EM更新作为扰动形式的标准梯度上升。利用这一特性,我们然后提供非渐近保证EM和梯度EM算法时,适用于一个有限集的样本。我们发展的后果,我们的一般理论的三个典型的例子不完全数据的问题:混合高斯,混合回归,和线性回归与协变量完全随机丢失。在每种情况下,我们的理论保证,通过适当的初始化,相对少量的EM(或梯度EM)步骤将产生(具有高概率)在MLE的统计误差范围内的估计。我们提供模拟来证实这种理论上预测的行为。

英文摘要:

We develop a general framework for proving rigorous guarantees on the performance of the EM algorithm and a variant known as gradient EM. Our analysis is divided into two parts: a treatment of these algorithms at the population level (in the limit of infinite data), followed by results that apply to updates based on a finite set of samples. First, we characterize the domain of attraction of any global maximizer of the population likelihood. This characterization is based on a novel view of the EM updates as a perturbed form of likelihood ascent, or in parallel, of the gradient EM updates as a perturbed form of standard gradient ascent. Leveraging this characterization, we then provide non-asymptotic guarantees on the EM and gradient EM algorithms when applied to a finite set of samples. We develop consequences of our general theory for three canonical examples of incomplete-data problems: mixture of Gaussians, mixture of regressions, and linear regression with covariates missing completely at random. In each case, our theory guarantees that with a suitable initialization, a relatively small number of EM (or gradient EM) steps will yield (with high probability) an estimate that is within statistical error of the MLE. We provide simulations to confirm this theoretically predicted behavior.

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