Statistics for Spatial Data.

1. Introduction and Overview. 2. Detecting Influential Observations and Outliers. 3. Detecting and Assessing Collinearity. 4. Applications and Remedies. 5. Research Issues and Directions for Extensions. Bibliography. Author Index. Subject Index.

Regression Diagnostics: Identifying Influential Data and Sources of Collinearity

SUMMARY Nonproportional hazards can often be expressed by extending the Cox model to include time varying coefficients; e.g., for a single covariate, the hazard function for subject i is modelled as exp { fl(t)Zi(t)}. A common example is a treatment effect that decreases with time. We show that the function /3(t) can be directly visualized by smoothing an appropriate residual plot. Also, many tests of proportional hazards, including those of Cox (1972), Gill & Schumacher (1987), Harrell (1986), Lin (1991), Moreau, O'Quigley & Mesbah (1985), Nagelkerke, Oosting & Hart (1984), O'Quigley & Pessione (1989), Schoenfeld (1980) and Wei (1984) are related to time-weighted score tests of the proportional hazards hypothesis, and can be visualized as a weighted least-squares line fitted to the residual plot.

Proportional hazards tests and diagnostics based on weighted residuals

In this book, Andrew Harvey sets out to provide a unified and comprehensive theory of structural time series models. Unlike the traditional ARIMA models, structural time series models consist explicitly of unobserved components, such as trends and seasonals, which have a direct interpretation. As a result the model selection methodology associated with structural models is much closer to econometric methodology. The link with econometrics is made even closer by the natural way in which the models can be extended to include explanatory variables and to cope with multivariate time series. From the technical point of view, state space models and the Kalman filter play a key role in the statistical treatment of structural time series models. The book includes a detailed treatment of the Kalman filter. This technique was originally developed in control engineering, but is becoming increasingly important in fields such as economics and operations research. This book is concerned primarily with modelling economic and social time series, and with addressing the special problems which the treatment of such series poses. The properties of the models and the methodological techniques used to select them are illustrated with various applications. These range from the modellling of trends and cycles in US macroeconomic time series to to an evaluation of the effects of seat belt legislation in the UK.

Forecasting, Structural Time Series Models and the Kalman Filter

Structured additive regression models are perhaps the most commonly used class of models in statistical applications. It includes, among others, (generalized) linear models, (generalized) additive models, smoothing spline models, state space models, semiparametric regression, spatial and spatiotemporal models, log-Gaussian Cox processes and geostatistical and geoadditive models. We consider approximate Bayesian inference in a popular subset of structured additive regression models, latent Gaussian models, where the latent field is Gaussian, controlled by a few hyperparameters and with non-Gaussian response variables. The posterior marginals are not available in closed form owing to the non-Gaussian response variables. For such models, Markov chain Monte Carlo methods can be implemented, but they are not without problems, in terms of both convergence and computational time. In some practical applications, the extent of these problems is such that Markov chain Monte Carlo sampling is simply not an appropriate tool for routine analysis. We show that, by using an integrated nested Laplace approximation and its simplified version, we can directly compute very accurate approximations to the posterior marginals. The main benefit of these approximations is computational: where Markov chain Monte Carlo algorithms need hours or days to run, our approximations provide more precise estimates in seconds or minutes. Another advantage with our approach is its generality, which makes it possible to perform Bayesian analysis in an automatic, streamlined way, and to compute model comparison criteria and various predictive measures so that models can be compared and the model under study can be challenged.

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Approximate Bayesian inference for latent Gaussian models by using integrated nested Laplace approximations

Introduction Stochastic simulation Introduction Generation of Discrete Random Quantities Generation of Continuous Random Quantities Generation of Random Vectors and Matrices Resampling Methods Exercises Bayesian Inference Introduction Bayes' Theorem Conjugate Distributions Hierarchical Models Dynamic Models Spatial Models Model Comparison Exercises Approximate methods of inference Introduction Asymptotic Approximations Approximations by Gaussian Quadrature Monte Carlo Integration Methods Based on Stochastic Simulation Exercises Markov chains Introduction Definition and Transition Probabilities Decomposition of the State Space Stationary Distributions Limiting Theorems Reversible Chains Continuous State Spaces Simulation of a Markov Chain Data Augmentation or Substitution Sampling Exercises Gibbs Sampling Introduction Definition and Properties Implementation and Optimization Convergence Diagnostics Applications MCMC-Based Software for Bayesian Modeling Appendix 5.A: BUGS Code for Example 5.7 Appendix 5.B: BUGS Code for Example 5.8 Exercises Metropolis-Hastings algorithms Introduction Definition and Properties Special Cases Hybrid Algorithms Applications Exercises Further topics in MCMC Introduction Model Adequacy Model Choice: MCMC Over Model and Parameter Spaces Convergence Acceleration Exercises References Author Index Subject Index

http://www.gbv.de/dms/goettingen/229627587.pdf

Markov Chain Monte Carlo: Stochastic Simulation for Bayesian Inference

Markov Chain Monte Carlo: Stochastic Simulation for Bayesian Inference, Second Edition

Generalized linear mixed models provide a unified framework for treatment of exponential family regression models, overdispersed data and longitudinal studies. These problems typically involve the presence of random effects and this paper presents a new methodology for making Bayesian inference about them. The approach is simulation-based and involves the use of Markov chain Monte Carlo techniques. The usual iterative weighted least squares algorithm is extended to include a sampling step based on the Metropolis–Hastings algorithm thus providing a unified iterative scheme. Non-normal prior distributions for the regression coefficients and for the random effects distribution are considered. Random effect structures with nesting required by longitudinal studies are also considered. Particular interests concern the significance of regression coefficients and assessment of the form of the random effects. Extensions to unknown scale parameters, unknown link functions, survival and frailty models are outlined.

Sampling from the posterior distribution in generalized linear mixed models

The aim of this paper is to analyse extremal events using generalized Pareto distributions (GPD), considering explicitly the uncertainty about the threshold. Current practice empirically determines...

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Bayesian analysis of extreme events with threshold estimation

There is a considerable literature in spatiotemporal modelling The approach adopted here applies to the setting where space is viewed as continuous but time is taken to be discrete We view the data as a time series of spatial processes and work in the setting of dynamic models, achieving a class of dynamic models for such data We seek rich, flexible, easy-to-specify, easy-to-interpret, computationally tractable specifications which allow very general mean structures and also non-stationary association structures

Our modelling contributions are as follows In the case where univariate data are collected at the spatial locations, we propose the use of a spatiotemporally varying coefficient form In the case where multivariate data are collected at the locations, we need to capture associations among measurements at a given location and time as well as dependence across space and time We propose the use of suitable multivariate spatial process models developed through coregionalization

We adopt a Bayesian inference framework The resulting posterior and predictive inference enables summaries in the form of tables and maps, which help to reveal the nature of the spatiotemporal behaviour as well as the associated uncertainty We illuminate various computational issues and then apply our models to the analysis of climate data obtained from the National Center for Atmospheric Research to analyze precipitation and temperature measurements obtained in Colorado in 1997 Copyright © 2005 John Wiley & Sons, Ltd

Dani Gamerman

Papers

Markov Chain Monte Carlo: Stochastic Simulation for Bayesian Inference

Markov Chain Monte Carlo: Stochastic Simulation for Bayesian Inference, Second Edition

Sampling from the posterior distribution in generalized linear mixed models

Bayesian analysis of extreme events with threshold estimation

Spatial process modelling for univariate and multivariate dynamic spatial data