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作者：Kume, Alfred
作者单位：University of Kent; University of Nottingham
摘要：A method is developed for fitting smooth curves through a series of shapes of landmarks in two dimensions using unrolling and unwrapping procedures in Riemannian manifolds. An explicit method of calculation is given which is analogous to that of Jupp & Kent ( 1987) for spherical data. The resulting splines are called shape-space smoothing splines. The method resembles that of fitting smoothing splines in real spaces in that, if the smoothing parameter is zero, the resulting curve interpolates ...
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作者：Falconer, Kenneth; Fernandez, Carmen
作者单位：University of St Andrews; Spanish Institute of Oceanography
摘要：We consider Bayesian inference via Markov chain Monte Carlo for a variety of fractal Gaussian processes on the real line. These models have unknown parameters in the covariance matrix, requiring inversion of a new covariance matrix at each Markov chain Monte Carlo iteration. The processes have no suitable independence properties so this becomes computationally prohibitive. We surmount these difficulties by developing a computational algorithm for likelihood evaluation based on a 'multiresoluti...
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作者：Glidden, David V.
作者单位：University of California System; University of California San Francisco
摘要：Frailty and copula models specify a parametric dependence structure for multivariate failure-time data. Estimation of some joint quantities can be highly sensitive to the assumed parametric form, and hence model fit is an important issue. This paper lays out a general diagnostic framework for evaluating and selecting frailty and copula models. The approach is based on the cumulative sum of residuals that are calculated in bivariate time. The residuals reflect the difference between the observe...
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作者：Taylor, J. E.; Worsley, K. J.; Gosselin, F.
作者单位：Stanford University; McGill University; Universite de Montreal
摘要：A smooth Gaussian random field with zero mean and unit variance is sampled on a discrete lattice, and we are interested in the exceedance probability or P-value of the maximum in a finite region. If the random field is smooth relative to the mesh size, then the P-value can be well approximated by results for the continuously sampled smooth random field (Adler, 1981; Worsley, 1995a; Taylor & Adler, 2003; Adler & Taylor, 2007). If the random field is not smooth, so that adjacent lattice values a...
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作者：Kuroki, Manabu
作者单位：University of Osaka
摘要：We consider the problem of using data in studies with an unobserved treatment/response variable in order to evaluate average causal effects, when cause-effect relationships between variables can be described by a directed acyclic graph and the corresponding recursive factorization of a joint distribution. The paper proposes graphical criteria to test whether average causal effects are identifiable even if a treatment/response variable is unobserved. If the answer is affirmative, we provide fur...
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作者：Bartolucci, Francesco; Pennoni, Fulvia
作者单位：University of Perugia; University of Milan
摘要：Following Cox & Wermuth ( 1994, 2002), we show that the distribution of a set of binary observable variables, induced by a certain discrete latent variable model, may be approximated by a quadratic exponential distribution. This discrete latent variable model is equivalent to the latent-class version of the two-parameter logistic model of Birnbaum ( 1968), which may be seen as a generalized version of the Rasch model ( Rasch, 1960, 1961). On the basis of this result, we develop an approximate ...
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作者：Lahiri, Soumendra N.; Maiti, Tapabrata; Katzoff, Myron; Parsons, Van
作者单位：Iowa State University; Centers for Disease Control & Prevention - USA; CDC National Center for Health Statistics (NCHS)
摘要：Best linear unbiased prediction is well known for its wide range of applications including small area estimation. While the theory is well established for mixed linear models and under normality of the error and mixing distributions, the literature is sparse for nonlinear mixed models under nonnormality of the error distribution or of the mixing distributions. We develop a resampling-based unified approach for predicting mixed effects under a generalized mixed model set-up. Second-order-accura...
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作者：Samia, Noelle I.; Chan, Kung-Sik; Stenseth, Nils Chr.
作者单位：University of Iowa; University of Oslo
摘要：We introduce the generalized threshold mixed model for piecewise-linear stochastic regression with possibly nonnormal time-series data. It is assumed that the conditional probability distribution of the response variable belongs to the exponential family, and the conditional mean response is linked to some piecewise-linear stochastic regression function. We study the particular case where the response variable equals zero in the lower regime. Some large-sample properties of a likelihood-based ...
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作者：Pourahmadi, Mohsen
作者单位：Northern Illinois University
摘要：Chen & Dunson (2003) have proposed a modified Cholesky decomposition of the form Sigma = DLL'D for a covariance matrix where D is a diagonal matrix with entries proportional to the square roots of the diagonal entries of Sigma and L is a unit lower-triangular matrix solely determining its correlation matrix. This total separation of variance and correlation is definitely a major advantage over the more traditional modified Cholesky decomposition of the form (LDL)-L-2' (Pourahmadi, 1999). We sh...
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作者：Cook, Dennis; Li, Bing; Chiaromonte, Francesca
作者单位：University of Minnesota System; University of Minnesota Twin Cities; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park
摘要：Regressions in which the fixed number of predictors p exceeds the number of independent observational units n occur in a variety of scientific fields. Sufficient dimension reduction provides a promising approach to such problems, by restricting attention to d < n linear combinations of the original p predictors. However, standard methods of sufficient dimension reduction require inversion of the sample predictor covariance matrix. We propose a method for estimating the central subspace that el...
