基于泛岭估计对岭估计过度压缩的改进方法

岭估计是解决多元线性回归多重共线性问题的有效方法,是有偏的压缩估计。与普通最小二乘估计相比,岭估计可以降低参数估计的均方误差,但是却增大残差平方和,拟合效果变差。本文提出一种基于泛岭估计对岭估计过度压缩的改进方法,可以改进岭估计的拟合效果,减小岭估计残差平方和的增加幅度。     

Minimax线性估计的影响分析

这里X是n×q列满秩阵,β是q×1未知参数,Y是n×1观察向量,e是n×1随机误差向量。估计β通常采用最小二乘估计(简记为LS估计)。但当设计矩阵X有复共线性存在时,的性能很不好。针对这个问题,近二十年来,特别是近十年来,许多统计学者相继提出了一些新的方法,企图改进LS估计。例如,Stein在1960年提出的压缩估计;Massy于1965年提出的主成分估计;Hoerl和Kennard于1970年提出的岭估计等。这些估计在均方误差的意义下     

基于多重共线性的处理方法

多重共线性简称共线性是多元线性回归分析中一个重要问题。消除共线性的危害一直是回归分析的一个重点。目前处理严重共线性的常用方法有以下几种:岭回归、主成分回归、逐步回归、偏最小二乘法、Lasso回归等。本文就这几种方法进行比较分析,介绍它们的优缺点,通过实例分析以便于选择合适的方法处理共线性。     

回归系数的稳健主成分估计

自变量间多元共线关系的存在以及数据集中离群值的存在,对回归系数最小二乘估计产生较大的影响。主成分估计用以抗多元共线,稳健M-估计具有抗离群值的特性。本文探讨了离群值对主成分估计的影响和多元共线对M-估计的影响。在此基础上提出了回归系数稳健主成分估计(RPC),RPC是主成分估计与M-估计的有机结合,它能同时抗离群值和多元共线并保留主成分估计与M-估计的优点。本文应用Monte-Carlo方法,考证了在多元共线与离群值同时存在时,RPC优于Ls估计、主成分估计和M-估计,说明RPC具有一定的实用价值。     

多元广义主成分估计类

本文提出了多元性模型中回归系统数阵的一个线性有偏估计类（称为多元广义主成分估计类），并讨论了它的种种优良性质。     

回归系数的stein型主成分估计

对于设计阵Ｘ呈病态的线性回归模型，本文提出了一种新的关于回归系数的有偏估计─ｓｔｅｉｎ型主成分估计，并在均方误差意义下，论证了在一定条件下ｓｔｅｉｎ型主成分估计优于主成分估计，因此也优于ｓｔｅｉｎ型ＯＬＳ估计与ＯＬＳ估计，最后，我们又对偏参数的存在性，最优性进行了讨论，并得出了一些重要结论．     

广义压缩最小二乘估计

本文引进了线性模型中回归系数的一个估计类。许多常用的估计,例如岭回归估计、主成分估计、压缩最小二乘估计以及迭代估计都属于这个估计类。本文讨论该估计类中估计的容许性问题以及矩阵均方误差准则下估计的比较问题。     

回归系数的改进主成分估计

本文提出一种新的主成分概念,确立相应的主成分选取原则,较大地改进了W.F.Massy的主成分方法;通过误差分析,证明本文的方法在一些情况下优于其他有偏估计方法。     

齐次线性约束回归模型参数的主成分压缩估计

当设计矩阵X复共线时,对齐次线性约束回归模型参数的约束最小二乘估计进行改进,提出参数的主成分压缩估计,并对新参数估计的性质进行了讨论,最后进行了数值模拟,验证了算法的参数估计优于约束最小二乘估计.     

稳健主成分聚类方法的构建及其比较研究

传统的主成分聚类方法往往会因对离群值比较敏感而导致聚类的结果与实际不相符。针对这一现象,本文运用稳健统计量对传统主成分聚类方法进行修正,构建出稳健主成分聚类分析算法,以克服离群值对模型计算结果的影响。由模拟和实证分析的计算结果可得知:当数据中没有离群值时,稳健主成分聚类方法的结果与传统主成分聚类方法一致;但当数据中有离群值时,相对于传统主成分聚类方法而言,稳健主成分聚类方法能有效抵抗离群值的影响,具有良好的抗干扰性和高抗差性。     

Robust model selection criteria for robust Liu estimator

In linear regression analysis, outliers often have large influence in the model/variable selection process. The aim of this study is to select the subsets of independent variables which explain dependent variables in the presence of multicollinearity, outliers and possible departures from the normality assumption of the error distribution in robust regression analysis. In this study to overcome this combined problem of multicollinearity and outliers, we suggest to use robust selection criterion with Liu and Liu-type M(LM) estimators.     

一类基于秩次的稳健线性回归估计与诊断方法

线性回归模型的误差项不服从正态分布或存在多个离群点时,可以将残差秩次的某些函数作为权重引入估计模型来减少离群点的不良影响。本文从参数估计、稳健性质、回归诊断等方面对基于残差秩次的一类稳健回归方法进行介绍.通过模拟研究和实例分析表明,R和GR估计是一种估计效率较高的稳健回归方法,其中GR估计可同时避免X与Y空间离群点,而高失效点HBR估计可通过控制某个参数在稳健性与估计效率之间进行折衷.     

Rank-based Liu regression

Due to the complicated mathematical and nonlinear nature of ridge regression estimator, Liu (Linear-Unified) estimator has been received much attention as a useful method to overcome the weakness of the least square estimator, in the presence of multicollinearity. In situations where in the linear model, errors are far away from normal or the data contain some outliers, the construction of Liu estimator can be revisited using a rank-based score test, in the line of robust regression. In this paper, we define the Liu-type rank-based and restricted Liu-type rank-based estimators when a sub-space restriction on the parameter of interest holds. Accordingly, some improved estimators are defined and their asymptotic distributional properties are investigated. The conditions of superiority of the proposed estimators for the biasing parameter are given. Some numerical computations support the findings of the paper.     

变系数部分线性模型的加权随机约束s-K估计

研究随机约束条件下半参数变系数部分线性模型的参数估计问题,当回归模型线性部分变量存在多重共线性时,基于Profile最小二乘方法、s-K估计和加权混合估计构造参数向量的加权随机约束s-K估计,并在均方误差矩阵准则下给出新估计量优于s-K估计和加权混合估计的充要条件,最后通过蒙特卡洛数值模拟验证所提出估计量的有限样本性质.     

Parameter estimation by Hellinger type distance for multivariate distributions based upon probability generating functions

Maximum likelihood (ML) estimation is a popular method for parameter estimation when modeling discrete or count observations but unfortunately it may be sensitive to outliers. Alternative robust methods like minimum Hellinger distance (MHD) have been proposed for estimation. However, in the multivariate case, the MHD method leads to computer intensive estimation especially when the joint probability density function is complicated. In this paper, a Hellinger type distance measure based on the probability generating function is proposed as a tool for quick and robust parameter estimation. The proposed method yields consistent estimators, performs well for simulated and real data, and can be computationally much faster than ML or MHD estimation.     

Composite Quantile Estimation in Partial Functional Linear Regression Model Based on Polynomial Spline

In this paper, we consider composite quantile regression for partial functional linear regression model with polynomial spline approximation. Under some mild conditions, the convergence rates of the estimators and mean squared prediction error, and asymptotic normality of parameter vector are obtained. Simulation studies demonstrate that the proposed new estimation method is robust and works much better than the least-squares based method when there are outliers in the dataset or the random error follows heavy-tailed distributions. Finally, we apply the proposed methodology to a spectroscopic data sets to illustrate its usefulness in practice.     

Outlier Detections in Autoregressive Models

This article proposes a new technique for detecting outliers in autoregressive models and identifying the type as either innovation or additive. This technique can be used without knowledge of the true model order, outlier location, or outlier type. Specifically, we perturb an observation to obtain the perturbation size that minimizes the resulting residual sum of squares (SSE). The reduction in the SSE yields outlier detection and identification measures. In addition, the perturbation size can be used to gauge the magnitude of the outlier. Monte Carlo studies and empirical examples are presented to illustrate the performance of the proposed method as well as the impact of outliers on model selection and parameter estimation. We also obtain robust estimators and model selection criteria, which are shown in simulation studies to perform well when large outliers occur.     

Mallows’ quasi-likelihood estimation for log-linear Poisson autoregressions

We consider the problems of robust estimation and testing for a log-linear model with feedback for the analysis of count time series. We study inference for contaminated data with transient shifts, level shifts and additive outliers. It turns out that the case of additive outliers deserves special attention. We propose a robust method for estimating the regression coefficients in the presence of interventions. The resulting robust estimators are asymptotically normally distributed under some regularity conditions. A robust score type test statistic is also examined. The methodology is applied to real and simulated data.     

A Class of Robust Principal Component Vectors

This paper is concerned with a study of robust estimation in principal component analysis. A class of robust estimators which are characterized as eigenvectors of weighted sample covariance matrices is proposed, where the weight functions recursively depend on the eigenvectors themselves. Also, a feasible algorithm based on iterative reweighting of the covariance matrices is suggested for obtaining these estimators in practice. Statistical properties of the proposed estimators are investigated in terms of sensitivity to outliers and relative efficiency via their influence functions, which are derived with the help of Stein's lemma. We give a simple condition on the weight functions which ensures robustness of the estimators. The class includes, as a typical example, a method by the self-organizing rule in the neural computation. A numerical experiment is conducted to confirm a rapid convergence of the suggested algorithm.     

Robust Estimation for Generalized Additive Models

This article studies M-type estimators for fitting robust generalized additive models in the presence of anomalous data. A new theoretical construct is developed to connect the costly M-type estimation with least-squares type calculations. Its asymptotic properties are studied and used to motivate a computational algorithm. The main idea is to decompose the overall M-type estimation problem into a sequence of well-studied conventional additive model fittings. The resulting algorithm is fast and stable, can be paired with different nonparametric smoothers, and can also be applied to cases with multiple covariates. As another contribution of this article, automatic methods for smoothing parameter selection are proposed. These methods are designed to be resistant to outliers. The empirical performance of the proposed methodology is illustrated via both simulation experiments and real data analysis. Supplementary materials are available online.