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Finding an unconstrained and statistically interpretable reparameterization of a covariance matrix is still an open problem in statistics. Its solution is of central importance in covariance estimation, particularly in the recent…

Methodology · Statistics 2012-02-09 Mohsen Pourahmadi

Statistical analysis on compositional data has gained a lot of attention due to their great potential of applications. A feature of these data is that they are multivariate vectors that lie in the simplex, that is, the components of each…

We develop a multi-level restricted Gaussian maximum likelihood method for estimating the covariance function parameters and computing the best unbiased predictor. Our approach produces a new set of multi-level contrasts where the…

Computation · Statistics 2016-03-29 Julio E. Castrillon-Candas , Marc G. Genton , Rio Yokota

Longitudinal studies are often conducted to explore the cohort and age effects in many scientific areas. The within cluster correlation structure plays a very important role in longitudinal data analysis. This is because not only can an…

Statistics Theory · Mathematics 2008-12-18 Yan Sun , Wenyang Zhang , Howell Tong

Missing data theory deals with the statistical methods in the occurrence of missing data. Missing data occurs when some values are not stored or observed for variables of interest. However, most of the statistical theory assumes that data…

The aim of reduced rank regression is to connect multiple response variables to multiple predictors. This model is very popular, especially in biostatistics where multiple measurements on individuals can be re-used to predict multiple…

Methodology · Statistics 2022-06-20 The Tien Mai , Pierre Alquier

Generalized Linear Models are routinely used in data analysis. The classical procedures for estimation are based on Maximum Likelihood and it is well known that the presence of outliers can have a large impact on this estimator. Robust…

Computation · Statistics 2017-10-02 Marina Valdora , Claudio Agostinelli , Victor J. Yohai

In our paper, we focus on robust variable selection for missing data and measurement error. Missing data and measurement errors can lead to confusing data distribution. We propose an exponential loss function with a tuning parameter to…

Methodology · Statistics 2025-07-01 Zhenhao Zhang , Yunquan Song

Missing data is pervasive in econometric applications, and rarely is it plausible that the data are missing (completely) at random. This paper proposes a methodology for studying the robustness of results drawn from incomplete datasets.…

Econometrics · Economics 2025-12-29 Daniel Ober-Reynolds

Positive semi-definite matrices commonly occur as normal matrices of least squares problems in statistics or as kernel matrices in machine learning and approximation theory. They are typically large and dense. Thus algorithms to solve…

Numerical Analysis · Mathematics 2020-12-01 Markus Hegland , Frank deHoog

This paper considers an empirical likelihood inference for parameters defined by general estimating equations, when data are missing at random. The efficiency of existing estimators depends critically on correctly specifying the conditional…

Methodology · Statistics 2016-12-06 Tianqing Liu , Xiaohui Yuan , Zhaohai Li , Aiyi Liu

We study the dynamics of matrix-valued time series with observed network structures by proposing a matrix network autoregression model with row and column networks of the subjects. We incorporate covariate information and a low rank…

Methodology · Statistics 2023-02-07 Xuening Zhu , Feifei Wang , Zeng Li , Yanyuan Ma

Covariance matrix estimation is one of the most important problems in statistics. To accommodate the complexity of modern datasets, it is desired to have estimation procedures that not only can incorporate the structural assumptions of…

Statistics Theory · Mathematics 2017-06-13 Mengjie Chen , Chao Gao , Zhao Ren

Estimating the disturbance or clutter covariance is a centrally important problem in radar space time adaptive processing (STAP). The disturbance covariance matrix should be inferred from training sample observations in practice. Large…

Applications · Statistics 2016-02-22 Bosung Kang

We consider the problem of estimating covariance and precision matrices, and their associated discriminant coefficients, from normal data when the rank of the covariance matrix is strictly smaller than its dimension and the available sample…

Statistics Theory · Mathematics 2015-09-09 Didier Chételat , Martin T. Wells

Gaussian mixtures are commonly used for modeling heavy-tailed error distributions in robust linear regression. Combining the likelihood of a multivariate robust linear regression model with a standard improper prior distribution yields an…

Statistics Theory · Mathematics 2023-01-05 Haoxiang Li , Qian Qin , Galin L. Jones

Motivated by graphical models, we consider the "Sparse Plus Low-rank" decomposition of a positive definite concentration matrix -- the inverse of the covariance matrix. This is a classical problem for which a rich theory and numerical…

Optimization and Control · Mathematics 2019-01-31 Valentina Ciccone , Augusto Ferrante , Mattia Zorzi

We consider the problem of joint estimation of structured inverse covariance matrices. We perform the estimation using groups of measurements with different covariances of the same unknown structure. Assuming the inverse covariances to span…

Machine Learning · Statistics 2015-11-23 Ilya Soloveychik , Ami Wiesel

How can we discern whether the covariance operator of a stochastic process is of reduced rank, and if so, what its precise rank is? And how can we do so at a given level of confidence? This question is central to a great deal of methods for…

Methodology · Statistics 2020-08-11 Anirvan Chakraborty , Victor M. Panaretos

In this paper we recast the problem of missing values in the covariates of a regression model as a latent Gaussian Markov random field (GMRF) model in a fully Bayesian framework. Our proposed approach is based on the definition of the…

Computation · Statistics 2019-12-24 Virgilio Gómez-Rubio , Michela Cameletti , Marta Blangiardo