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Clustering in linear mixed models with approximate Dirichlet process mixtures using EM algorithm
 Statistical Modelling
"... Abstract: In linear mixedmodels, the assumption of normally distributed random effects is often inappropriate and unnecessarily restrictive. The proposed approximate Dirichlet process mixture assumes a hierarchical Gaussian mixture that is based on the truncated version of the stick breaking presen ..."
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Abstract: In linear mixedmodels, the assumption of normally distributed random effects is often inappropriate and unnecessarily restrictive. The proposed approximate Dirichlet process mixture assumes a hierarchical Gaussian mixture that is based on the truncated version of the stick breaking presentation of the Dirichlet process. In addition to the weakening of distributional assumptions, the specification allows to identify clusters of observations with a similar random effects structure. An ExpectationMaximization algorithm is given that solves the estimation problem and that, in certain respects, may exhibit advantages over Markov chain Monte Carlo approaches when modelling with Dirichlet processes. The method is evaluated in a simulation study and applied to the dynamics of unemployment in Germany as well as lung function growth data.
Extensions of the BartlettLewis Model for Rainfall Processes
 Statistical Modelling
"... Abstract: While the Bartlett–Lewis model has been widely used for modelling rainfall processes at a xed point in space over time, there are observed features, such as longerscale dependence, which are not well tted by the model. In this paper, we study an extension where we put an extra layer in th ..."
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Abstract: While the Bartlett–Lewis model has been widely used for modelling rainfall processes at a xed point in space over time, there are observed features, such as longerscale dependence, which are not well tted by the model. In this paper, we study an extension where we put an extra layer in the clustered Poisson process of storm origins. We also investigate the Pareto interarrival time for the storm origins, which has been used to model webtrafc data. We derive the theoretical rst and secondorder properties of the multilayer clustered Poisson processes, but generally we have to rely on Monte Carlo techniques. The models are tted to hourly rainfall data from Valentia observatory in southwest Ireland, where the extensions are shown to improve on the standard models. We generalize these models further by allowing some parameters of the models to be a function of some covariates. An application using data from Valentia observatory and Belmullet shows how to use this class of models to analyze the association between the rainfall pattern and the North Atlantic Oscillation (NAO) index.
Estimating Incidence Curves of Several Infections Using Symptom Surveillance Data
, 2011
"... We introduce a method for estimating incidence curves of several cocirculating infectious pathogens, where each infection has its own probabilities of particular symptom profiles. Our deconvolution method utilizes weekly surveillance data on symptoms from a defined population as well as additional ..."
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We introduce a method for estimating incidence curves of several cocirculating infectious pathogens, where each infection has its own probabilities of particular symptom profiles. Our deconvolution method utilizes weekly surveillance data on symptoms from a defined population as well as additional data on symptoms from a sample of virologically confirmed infectious episodes. We illustrate this method by numerical simulations and by using data from a survey conducted on the
Haplotypes with Copy Number and Single Nucleotide Polymorphisms in CYP2A6 Locus Are Associated with Smoking Quantity in a Japanese Population
, 2012
"... Smoking is a major public health problem, but the genetic factors associated with smoking behaviors are not fully elucidated. Here, we have conducted an integrated genomewide association study to identify common copy number polymorphisms (CNPs) and single nucleotide polymorphisms (SNPs) associated ..."
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Smoking is a major public health problem, but the genetic factors associated with smoking behaviors are not fully elucidated. Here, we have conducted an integrated genomewide association study to identify common copy number polymorphisms (CNPs) and single nucleotide polymorphisms (SNPs) associated with the number of cigarettes smoked per day (CPD) in Japanese smokers (N = 17,158). Our analysis identified a common CNP with a strong effect on CPD (rs8102683; P~3:810{42) in the 19q13 region, encompassing the CYP2A6 locus. After adjustment for the associated CNP, we found an additional associated SNP (rs11878604; P~9:710{30) located 30 kb downstream of the CYP2A6 gene. Imputation of the CYP2A6 locus revealed that haplotypes underlying the CNP and the SNP corresponded to classical, functional alleles of CYP2A6 gene that regulate nicotine metabolism and explained 2 % of the phenotypic variance of CPD (ANOVA Ftest P~9:510{52). These haplotypes were also associated with smokingrelated diseases, including lung cancer, chronic
BMC Systems Biology BioMed Central Research article Inference of gene pathways using mixture Bayesian networks
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Hans Åhlfeldt1, Nosrat Shahsavar1,5 and the SouthEast Swedish Breast Cancer Study Group
, 2005
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International Journal of Health
, 2009
"... This is an Open Access article distributed under the terms of the Creative Commons Attribution License ..."
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This is an Open Access article distributed under the terms of the Creative Commons Attribution License
STATISTICS IN MEDICINE
"... Modelling the distribution of ischaemic strokespeci c survival time using an EMbased mixture approach with random e ects adjustment ..."
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Modelling the distribution of ischaemic strokespeci c survival time using an EMbased mixture approach with random e ects adjustment
Incremental update; Length of stay; Machine learning
"... An incremental EMbased learning approach for online prediction of hospital resource utilization ..."
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An incremental EMbased learning approach for online prediction of hospital resource utilization