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arXiv 1501.02497math.STstat.MLstat.TH
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有限混合体中多类参数的可辨识性和最优收敛速度

Identifiability and optimal rates of convergence for parameters of multiple types in finite mixtures

Nhat Ho, XuanLong Nguyen

摘要:

本文研究了有限混合模型中多类型参数的可辨识性和收敛性,以及含有混合分量的模型拟合的影响。首先,我们提出了一个强可识别性的一般理论,它扩展了Nguyen [2013]和Chen [1995]以前的工作,以解决广泛的混合模型和处理矩阵变量参数。这些模型共享相同的Wasserstein距离为基础的最佳收敛速度的混合分布的空间-$n^{-1/2}$下$W_1$的精确拟合和$n^{-1/4}$下$W_2$的过度拟合设置,其中$n$是样本量。然而,这一理论并不适用于几个重要的模型类,包括位置尺度多元高斯混合,形状尺度伽玛混合和位置尺度形状斜态混合。这项工作的第二部分是致力于证明这些“弱识别”类,密度族的代数结构在确定模型参数的收敛速度,这显示了非常丰富的行为谱中发挥了根本性的作用。例如,在过拟合的位置协方差高斯混合物中的参数估计的最佳速率由多项式方程的可解系统的阶数精确地确定--当更多的额外分量被添加到模型中时,这些速率迅速恶化。各种设置的既定利率说明了模拟研究。

英文摘要:

This paper studies identifiability and convergence behaviors for parameters of multiple types in finite mixtures, and the effects of model fitting with extra mixing components. First, we present a general theory for strong identifiability, which extends from the previous work of Nguyen [2013] and Chen [1995] to address a broad range of mixture models and to handle matrix-variate parameters. These models are shown to share the same Wasserstein distance based optimal rates of convergence for the space of mixing distributions --- $n^{-1/2}$ under $W_1$ for the exact-fitted and $n^{-1/4}$ under $W_2$ for the over-fitted setting, where $n$ is the sample size. This theory, however, is not applicable to several important model classes, including location-scale multivariate Gaussian mixtures, shape-scale Gamma mixtures and location-scale-shape skew-normal mixtures. The second part of this work is devoted to demonstrating that for these "weakly identifiable" classes, algebraic structures of the density family play a fundamental role in determining convergence rates of the model parameters, which display a very rich spectrum of behaviors. For instance, the optimal rate of parameter estimation in an over-fitted location-covariance Gaussian mixture is precisely determined by the order of a solvable system of polynomial equations --- these rates deteriorate rapidly as more extra components are added to the model. The established rates for a variety of settings are illustrated by a simulation study.

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。

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