On the Maximum Likelihood Estimation of a Covariance Matrix

For a multivariate normal set-up, it is well known that themaximumlikelihood estimator (MLE) of covariance matrix is neither admissible nor minimax under the Stein loss function. In this paper, we reveal that the MLE based on the Iwasawa parameterization leads to minimaxity with respect to the Stein loss function. Furthermore, a novel class of loss functions is proposed so that the minimum risks of the MLEs are identical in different coordinate systems, Cholesky parameterization and full Iwasawa parameterization. In other words, the MLEs based on these two different parameterizations are characterized by the property of minimaxity, without a Stein paradox. The application of our novel method to the high-dimensional covariance matrix problem is also discussed.     

最大似然估计的一个推广

我们常常会遇到最大似然估计不存在的情况,这种情况以在非正态回归模型中最为典型。当参数向量不能被估计时,人们对参数向量的线性函数的估计饶有兴趣。本文给出了这些线性函数的广义最大似然估计的定义,讨论了它的性质,并得到了利用投影变换确定具有有限广义最大似然估计的线性函数的方法。最后,通过几个常见的定性资料统计模型的实例,展现了求广义最大似然估计的实施过程。     

初始值外生给定下动态空间面板数据模型的拟极大似然估计

基于初始值外生性假定,本文构建的动态空间面板数据固定效应模型内含空间自相关和空间误差两种结构,并采用拟极大似然方法推导模型参数具有渐近性质和渐近分布的估计量;进一步,蒙特卡洛模拟实验结果显示,本文所推导的拟极大似然估计量呈现的统计特征与理论结论一致,即具有随样本容量的增加而不断改进的渐近性质;分别讨论模型中存在的时间和空间两类维度的变化影响发现,参数估计量的渐近表现对时间维度的变化较为敏感,在空间维度难以增加情形下,时间维度的有效增加能够有效地提高参数估计量性质。     

Maximum Likelihood Estimation for an Observation Driven Model for Poisson Counts

This paper is concerned with an observation-driven model for time series of counts whose conditional distribution given past observations follows a Poisson distribution.This class of models is capable of modeling a wide range of dependence structures and is readily estimated using an approximation to the likelihood function. Recursive formulae for carrying out maximum likelihood estimation are provided and the technical components required for establishing a central limit theorem of the maximum likelihood estimates are given in a special case.AMS 2000 Subject Classification: Primary 62M05; Secondary 62E20     

参数θ的函数f(θ)的极大似然估计

在微积分范围内给出了参数θ的函数f(θ)的极大似然估计.     

Approximate Maximum Likelihood Estimation of Circle Parameters

The estimation of a circles centre and radius from a set of noisy measurements of its circumference has many applications. It is a problem of fitting a circle to the measurements and the fit can be in algebraic or geometric distances. The former gives linear equations, while the latter yields nonlinear equations. Starting from estimation theory, this paper first proves that the maximum likelihood (ML), i.e., the optimal estimation of the circle parameters, is equivalent to the minimization of the geometric distances. It then derives a pseudolinear set of ML equations whose coefficients are functions of the unknowns. An approximate ML algorithm updates the coefficients from the previous solution and selects the solution that gives the minimum cost. Simulation results show that the ML algorithm attains the Cramer-Rao lower bound (CRLB) for arc sizes as small as 90°. For arc sizes of 15° and 5° the ML algorithm errors are slightly above the CRLB, but lower than those of other linear estimators.Communicated by L. C. W. Dixon     

Maximum Likelihood Estimation of Asymmetric Laplace Parameters

Maximum likelihood estimators (MLE's) are presented for the parameters of a univariate asymmetric Laplace distribution for all possible situations related to known or unknown parameters. These estimators admit explicit form in all but two cases. In these exceptions effective algorithms for computing the estimators are provided. Asymptotic distributions of the estimators are given. The asymptotic normality and consistency of the MLE's for the scale and location parameters are derived directly via representations of the relevant random variables rather than from general sufficient conditions for asymptotic normality of the MLE's.     

基于离散观测下Cauchy-OU过程的最大似然估计

基于离散观测样本,本文研究Cauchy-OU过程的参数估计问题.在大多数情况下,离散时间的最大似然函数是不能直接计算出来的,因此采用傅里叶变换及Gaver-Stehfest算法,构造似然函数的一个显式逼近序列,且该序列收敛于真实(但未知)的似然函数.最后,采用最大似然估计法估计出未知参数.仿真实验表明,所得到的参数估计是比较准确且稳定的.     

有关顺序统计量的极大似然估计

讨论了一类参数空间受样本限制的极大似然估计问题.分析了随机变量分布的非零区域与似然函数定义域的对应关系,提出如果分布的非零区域受参数限制,则无论似然方程是否可解,参数的极大似然估计必然与样本顺序统计量X_((n))或X_((1))有关,并具体分析了似然估计一定等于、一定不等于和可能等于顺序统计量X_((n))(X_((1)))的三种情形,并给出了相应的判别条件.最后分析得出在第三种判别条件之下,似然估计是否取值于x_((n))(x_((1)))视具体的样本观测值决定.     

基于GARCH模型的期望损失ES非参数核估计

风险度量ES最新的非参数估计方法,不依赖于分布假设,但不能动态反应金融时间序列的风险.针对金融时间序列的波动,结合GARCH模型进行期望损失ES的非参数核估计,得到随市场波动而动态变化的ES预测.通过数值模拟和对近两年的上证指数实证分析验证了该方法能准确而有效的反映市场风险.     

基于多维名义模型的加权似然估计方法(英文)

The Monte Carlo study evaluates the relative accuracy of Warm's (1989) weighted likelihood estimate (WLE) compared to the maximum likelihood estimate (MLE) using the nominal response model. And the results indicate that WLE was more accurate than MLE.     

Sequential Maximum Likelihood Estimation for the Squared Radial Ornstein-Uhlenbeck Process

In this paper, we study the properties of a sequential maximum likelihood estimator of the unknown parameter for the squared radial Ornstein-Uhlenbeck process. The estimator is proved to be closed, unbiased, normally distributed and strongly consistent. Lastly a simulation study is presented to illustrate the efficiency of the estimators.

     

二元Kundu-Gupta型二点分布参数的最大似然估计

讨论二元Kundu-Gupta型二点分布的识别性及参数估计,已知可识最小值的分布时,则参数可识别;由此得到了参数的最大似然估计;其中二个参数的估计量是无偏的,另外一个参数的估计量的期望不存在;模拟结果显示:估计值均稳定于真值参数.     

线性度量误差模型的极大经验似然估计

本文将自变量的测量误差考虑到线性模型中,提出了线性度量误差模型参数的极大经验似然估计,在一定条件下,证明了所得到的未知参数的估计具有渐进正态性,并通过数值模拟,说明了该方法的可行性。     

Maximum Likelihood Estimation of Hidden Markov Multivariate Normal Distribution Parameters

Hidden Markov model is widely used in statistical modeling of time, space and state transition data. The definition of hidden Markov multivariate normal distribution is given. The principle of using cluster analysis to determine the hidden state of observed variables is introduced. The maximum likelihood estimator of the unknown parameters in the model is derived. The simulated observation data set is used to test the estimation effect and stability of the method. The characteristic is simple classical statistical inference such as cluster analysis and maximum likelihood estimation. The method solves the parameter estimation problem of complex statistical models.     

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??Hidden Markov model is widely used in statistical modeling of time, space and state transition data. The definition of hidden Markov multivariate normal distribution is given. The principle of using cluster analysis to determine the hidden state of observed variables is introduced. The maximum likelihood estimator of the unknown parameters in the model is derived. The simulated observation data set is used to test the estimation effect and stability of the method. The characteristic is simple classical statistical inference such as cluster analysis and maximum likelihood estimation. The method solves the parameter estimation problem of complex statistical models.     

一类零膨胀广义线性模型极大似然估计的相合性与渐近正态性

讨论了响应变量为单参数指数族且在零点处膨胀的广义线性模型的大样本性质,对其参数进行了极大似然估计,给出了一些正则条件.基于所提出的正则条件,证明了模型参数极大似然估计的相合性与渐近正态性.     

Maximum Likelihood Estimation of Isotonic Normal Means with Unknown Variances

To analyze the isotonic regression problem for normal means, it is usual to assume that all variances are known or unknown but equal. This paper then studies this problem in the case that there are no conditions imposed on the variances. Suppose that we have data drawn fromkindependent normal populations with unknown meansμ_i's and unknown variancesσ²_i's, in which the means are restricted by a given partial ordering. This paper discusses some properties of the maximum likelihood estimates ofμ_i's andσ²_i's under the restriction and proposes an algorithm for obtaining the estimates.     

Bayesian and Maximum Likelihood Estimation for Gaussian Processes on an Incomplete Lattice

This article proposes a new approach for Bayesian and maximum likelihood parameter estimation for stationary Gaussian processes observed on a large lattice with missing values. We propose a Markov chain Monte Carlo approach for Bayesian inference, and a Monte Carlo expectation-maximization algorithm for maximum likelihood inference. Our approach uses data augmentation and circulant embedding of the covariance matrix, and provides likelihood-based inference for the parameters and the missing data. Using simulated data and an application to satellite sea surface temperatures in the Pacific Ocean, we show that our method provides accurate inference on lattices of sizes up to 512 × 512, and is competitive with two popular methods: composite likelihood and spectral approximations.