A semiparametric approach to simultaneous covariance estimation for bivariate sparse longitudinal data.
A semiparametric approach to simultaneous covariance estimation for bivariate sparse longitudinal data.
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DOI：
10.1111/biom.12133
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发表时间：
2014-03
期刊：
影响因子：
1.9
通讯作者：
Daniels MJ
中科院分区：
文献类型：
--
作者：
Das K;Daniels MJ
Estimation of the covariance structure for irregular sparse longitudinal data has been studied by many authors in recent years but typically using fully parametric specifications. In addition, when data are collected from several groups over time, it is known that assuming the same or completely different covariance matrices over groups can lead to loss of efficiency and/or bias. Nonparametric approaches have been proposed for estimating the covariance matrix for regular univariate longitudinal data by sharing information across the groups under study. For the irregular case, with longitudinal measurements that are bivariate or multivariate, modeling becomes more difficult. In this article, to model bivariate sparse longitudinal data from several groups, we propose a flexible covariance structure via a novel matrix stick-breaking process for the residual covariance structure and a Dirichlet process mixture of normals for the random effects. Simulation studies are performed to investigate the effectiveness of the proposed approach over more traditional approaches. We also analyze a subset of Framingham Heart Study data to examine how the blood pressure trajectories and covariance structures differ for the patients from different BMI groups (high, medium and low) at baseline.
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影响因子：
2
作者：
Das, Kiranmoy;Li, Jiahan;Fu, Guifang;Wang, Zhong;Li, Runze;Wu, Rongling
通讯作者：
Wu, Rongling
影响因子：
2.7
作者：
Wu, WB;Pourahmadi, M
通讯作者：
Pourahmadi, M
DOI：
10.1016/s0169-2607(02)00017-2
发表时间：
2002-11-01
影响因子：
6.1
作者：
Thiébaut, R;Jacqmin-Gadda, H;Commenges, D
通讯作者：
Commenges, D
影响因子：
2
作者：
Das, Kiranmoy;Li, Runze;Wu, Rongling
通讯作者：
Wu, Rongling
DOI：
10.1198/016214501750332758
发表时间：
2001-03-01
影响因子：
3.7
作者：
Ishwaran, H;James, LF
通讯作者：
James, LF