Journal ArticleTest · March 1, 2024
Quantile regression continues to increase in usage, providing a useful alternative to customary mean regression. Primary implementation takes the form of so-called multiple quantile regression, creating a separate regression for each quantile of interest. ...
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Journal ArticleMethods in Ecology and Evolution · January 1, 2024
Turnover, or change in the composition of species over space and time, is one of the primary ways to define beta diversity. Inferring what factors impact beta diversity is not only important for understanding biodiversity processes but also for conservatio ...
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Journal ArticleInternational Journal of Climatology · December 30, 2023
There is continuing interest in the investigation of change in temperature over space and time. For this analysis, we offer statistical tools to illuminate changes temporally, at desired temporal resolution, and spatially, using data generated from suitabl ...
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Journal ArticleEnvironmental and Ecological Statistics · December 1, 2023
An important objective for marine biologists is to forecast the distribution and abundance of planktivorous marine predators. To do so, it is critically important to understand the spatiotemporal dynamics of their prey. Here, the prey we study are zooplank ...
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Journal ArticleGlobal change biology · November 2023
Understanding community responses to climate is critical for anticipating the future impacts of global change. However, despite increased research efforts in this field, models that explicitly include important biological mechanisms are lacking. Quantifyin ...
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Journal ArticleEnvironmental and Ecological Statistics · September 1, 2023
The investigation of leaf-level traits in response to varying environmental conditions has immense importance for understanding plant ecology. Remote sensing technology enables measurement of the reflectance of plants to make inferences about underlying tr ...
Full textCite
Journal ArticleAnnals of Applied Statistics · September 1, 2023
Regression is the most widely used modeling tool in statistics. Quantile regression offers a strategy for enhancing the regression picture beyond cus-tomary mean regression. With time-series data, we move to quantile autore-gression and, finally, with spat ...
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Dataset · August 29, 2023
Understanding community responses to climate is critical for anticipating the future impacts of global change. However, despite increased research efforts in this field, models that explicitly include important biological mechanisms are lacking. Quantifyin ...
Full textCite
Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · March 1, 2023
A frequent challenge encountered with ecological data is how to interpret, analyze, or model data having a high proportion of zeros. Much attention has been given to zero-inflated count data, whereas models for non-negative continuous data with an abundanc ...
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Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · March 1, 2023
Understanding how communities respond to environmental change is frustrated by the fact that both species interactions and movement affect biodiversity in unseen ways. To evaluate the contributions of species interactions on community growth, dynamic model ...
Full textCite
Journal ArticleAnnals of Applied Statistics · March 1, 2023
Continuous time discrete state models are a valuable tool for explaining animal movement. However, data collection to fit such models over a spec-ified window of time can be misaligned with the actual realization of the movement process. This necessitates ...
Full textCite
Journal ArticleAnimal Biotelemetry · December 1, 2022
Background: As levels of anthropogenic noise in the marine environment rise, it is crucial to quantify potential associated effects on marine mammals. Yet measuring responses is challenging because most species spend the majority of their time submerged. C ...
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Journal ArticleSpatial Statistics · October 1, 2022
Preferential sampling provides a formal modeling specification to capture the effect of bias in a set of sampling locations on inference when a geostatistical model is used to explain observed responses at the sampled locations. In particular, it enables m ...
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Journal ArticleStochastic Environmental Research and Risk Assessment · September 1, 2022
Evidence of global warming induced from the increasing concentration of greenhouse gases in the atmosphere suggests more frequent warm days and heat waves. The concept of an extreme heat event (EHE), defined locally based on exceedance of a suitable local ...
Full textCite
Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · September 1, 2022
Acknowledging a considerable literature on modeling daily temperature data, we propose a multi-level spatiotemporal model which introduces several innovations in order to explain the daily maximum temperature in the summer period over 60 years in a region ...
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Journal ArticleAnnals of Applied Statistics · September 1, 2022
Plant reflectance spectra, the profile of light reflected by leaves across different wavelengths, supply the spectral signature for a species at a spatial location to enable estimation of functional and taxonomic diversity for plants. We consider leaf spec ...
Full textCite
Journal ArticleSpatial Statistics · August 1, 2022
Species distribution modeling is a primary ecological activity that has witnessed substantial evolution since the turn of the 21st century. For plant communities, two key features are the move from individual to joint species modeling and the move from reg ...
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Journal ArticleScandinavian Journal of Statistics · March 1, 2022
In this article, we propose a doubly stochastic spatial point process model with both aggregation and repulsion. This model combines the ideas behind Strauss processes and log Gaussian Cox processes. The likelihood for this model is not expressible in clos ...
Full textCite
Journal ArticleMethodology and Computing in Applied Probability · September 1, 2021
Generalized evolutionary point processes offer a class of point process models that allows for either excitation or inhibition based upon the history of the process. In this regard, we propose modeling which comprises generalization of the nonlinear Hawkes ...
Full textCite
Journal ArticleTest · March 1, 2024
Quantile regression continues to increase in usage, providing a useful alternative to customary mean regression. Primary implementation takes the form of so-called multiple quantile regression, creating a separate regression for each quantile of interest. ...
Full textCite
Journal ArticleMethods in Ecology and Evolution · January 1, 2024
Turnover, or change in the composition of species over space and time, is one of the primary ways to define beta diversity. Inferring what factors impact beta diversity is not only important for understanding biodiversity processes but also for conservatio ...
Full textCite
Journal ArticleInternational Journal of Climatology · December 30, 2023
There is continuing interest in the investigation of change in temperature over space and time. For this analysis, we offer statistical tools to illuminate changes temporally, at desired temporal resolution, and spatially, using data generated from suitabl ...
Full textCite
Journal ArticleEnvironmental and Ecological Statistics · December 1, 2023
An important objective for marine biologists is to forecast the distribution and abundance of planktivorous marine predators. To do so, it is critically important to understand the spatiotemporal dynamics of their prey. Here, the prey we study are zooplank ...
Full textCite
Journal ArticleGlobal change biology · November 2023
Understanding community responses to climate is critical for anticipating the future impacts of global change. However, despite increased research efforts in this field, models that explicitly include important biological mechanisms are lacking. Quantifyin ...
Full textCite
Journal ArticleEnvironmental and Ecological Statistics · September 1, 2023
The investigation of leaf-level traits in response to varying environmental conditions has immense importance for understanding plant ecology. Remote sensing technology enables measurement of the reflectance of plants to make inferences about underlying tr ...
Full textCite
Journal ArticleAnnals of Applied Statistics · September 1, 2023
Regression is the most widely used modeling tool in statistics. Quantile regression offers a strategy for enhancing the regression picture beyond cus-tomary mean regression. With time-series data, we move to quantile autore-gression and, finally, with spat ...
Full textCite
Dataset · August 29, 2023
Understanding community responses to climate is critical for anticipating the future impacts of global change. However, despite increased research efforts in this field, models that explicitly include important biological mechanisms are lacking. Quantifyin ...
Full textCite
Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · March 1, 2023
A frequent challenge encountered with ecological data is how to interpret, analyze, or model data having a high proportion of zeros. Much attention has been given to zero-inflated count data, whereas models for non-negative continuous data with an abundanc ...
Full textCite
Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · March 1, 2023
Understanding how communities respond to environmental change is frustrated by the fact that both species interactions and movement affect biodiversity in unseen ways. To evaluate the contributions of species interactions on community growth, dynamic model ...
Full textCite
Journal ArticleAnnals of Applied Statistics · March 1, 2023
Continuous time discrete state models are a valuable tool for explaining animal movement. However, data collection to fit such models over a spec-ified window of time can be misaligned with the actual realization of the movement process. This necessitates ...
Full textCite
Journal ArticleAnimal Biotelemetry · December 1, 2022
Background: As levels of anthropogenic noise in the marine environment rise, it is crucial to quantify potential associated effects on marine mammals. Yet measuring responses is challenging because most species spend the majority of their time submerged. C ...
Full textCite
Journal ArticleSpatial Statistics · October 1, 2022
Preferential sampling provides a formal modeling specification to capture the effect of bias in a set of sampling locations on inference when a geostatistical model is used to explain observed responses at the sampled locations. In particular, it enables m ...
Full textCite
Journal ArticleStochastic Environmental Research and Risk Assessment · September 1, 2022
Evidence of global warming induced from the increasing concentration of greenhouse gases in the atmosphere suggests more frequent warm days and heat waves. The concept of an extreme heat event (EHE), defined locally based on exceedance of a suitable local ...
Full textCite
Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · September 1, 2022
Acknowledging a considerable literature on modeling daily temperature data, we propose a multi-level spatiotemporal model which introduces several innovations in order to explain the daily maximum temperature in the summer period over 60 years in a region ...
Full textCite
Journal ArticleAnnals of Applied Statistics · September 1, 2022
Plant reflectance spectra, the profile of light reflected by leaves across different wavelengths, supply the spectral signature for a species at a spatial location to enable estimation of functional and taxonomic diversity for plants. We consider leaf spec ...
Full textCite
Journal ArticleSpatial Statistics · August 1, 2022
Species distribution modeling is a primary ecological activity that has witnessed substantial evolution since the turn of the 21st century. For plant communities, two key features are the move from individual to joint species modeling and the move from reg ...
Full textCite
Journal ArticleScandinavian Journal of Statistics · March 1, 2022
In this article, we propose a doubly stochastic spatial point process model with both aggregation and repulsion. This model combines the ideas behind Strauss processes and log Gaussian Cox processes. The likelihood for this model is not expressible in clos ...
Full textCite
Journal ArticleMethodology and Computing in Applied Probability · September 1, 2021
Generalized evolutionary point processes offer a class of point process models that allows for either excitation or inhibition based upon the history of the process. In this regard, we propose modeling which comprises generalization of the nonlinear Hawkes ...
Full textCite
Journal ArticleTest · September 1, 2021
We consider the setting of multivariate functional data collected over time at each of a set of sites. Our objective is to implement model-based clustering of the functions across the sites where we allow such clustering to vary over time. Anticipating dep ...
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Journal ArticleEnvironmental and Ecological Statistics · September 1, 2021
Citizen science databases are increasing in importance as sources of ecological information, but variability in effort across locations is inherent to such data. Spatially biased data—data not sampled uniformly across the study region—is expected. A furthe ...
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Journal ArticleInternational journal of environmental research and public health · September 2021
We develop a local, spatial measure of educational isolation (EI) and characterize the relationship between EI and our previously developed measure of racial isolation (RI). EI measures the extent to which non-college educated individuals are exposed prima ...
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Journal ArticleJournal of the Royal Statistical Society. Series A: Statistics in Society · July 1, 2021
There is increasing evidence that global warming manifests itself in more frequent warm days and that heat waves will become more frequent. Presently, a formal definition of a heat wave is not agreed upon in the literature. To avoid this debate, we conside ...
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Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · June 1, 2021
Understanding unexposed/baseline behavior of marine mammals is required to assess the effects of increasing levels of anthropogenic noise exposure in the marine environment. However, quantifying variation in the baseline behavior of whales is challenging d ...
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Journal ArticleEnvironmental and Ecological Statistics · June 1, 2021
Joint species distribution modeling is attracting increasing attention these days, acknowledging the fact that individual level modeling fails to take into account expected dependence/interaction between species. These joint models capture species dependen ...
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Journal ArticleSankhya B · May 1, 2021
Recently, extensions of the Dirichlet process to the functional domain have been presented in the literature. These processes can be classified based on the type of labeling they induce across different arguments in the domain, i.e., marginal or joint labe ...
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Chapter · January 1, 2021
Spatially-referenced multivariate data is becoming increasingly common. Here, we focus on data in the form of vectors observed at a finite set of spatial locations. Regression models are of interest in order to explain the response vectors as well as to pr ...
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Journal ArticleSpatial Statistics · August 1, 2020
For a given region, we have a dataset composed of car theft locations along with a linked dataset of recovery locations which, due to partial recovery, is a relatively small subset of the set of theft locations. For an investigator seeking to understand th ...
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Journal ArticleSpatial Statistics · June 1, 2020
The scope of spatial statistics problems arising in ecology is substantial. They concern both plant and animal behavior. Here, we discuss only plants. The range of issues is still very large and so we confine ourselves to four challenges, each within the c ...
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Journal ArticleJournal of the Royal Statistical Society. Series A: Statistics in Society · January 1, 2020
Hedonic models are widely used to predict selling prices of properties. Originally, they were proposed as simple spatial regressions, i.e. a spatially referenced response regressed on spatially referenced predictors. Subsequently, spatial random effects we ...
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Journal ArticleEcological Monographs · August 1, 2019
Presence/absence data and presence-only data are the two customary sources for learning about species distributions over a region. We present an ambitious agenda with regard to the analysis of such data. We illuminate the fundamental modeling differences b ...
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Journal ArticleSpatial Statistics · August 1, 2019
Isotropic covariance functions are routinely adopted in specifying models for point-referenced spatial data but carry the limitation that spatial dependence is not directional. Geometric anisotropic covariance functions offer a class of stationary specific ...
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Journal ArticleAmerican Statistician · July 3, 2019
Disease mapping focuses on learning about areal units presenting high relative risk. Disease mapping models assume that the disease counts are distributed as Poisson random variables with the respective means typically specified as the product of the relat ...
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Journal ArticleJournal of the Royal Statistical Society. Series A: Statistics in Society · June 1, 2019
Ground level ozone and particulate matter pollutants are associated with a variety of health issues and increased mortality. For this reason, Mexican environmental agencies regulate pollutant levels. In addition, Mexico City defines pollution emergencies b ...
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Journal ArticleSpatial Statistics · March 1, 2019
Point patterns gathered over space and time are receiving increasing attention in the literature. Examples include incidence of disease events, incidence of insurgent activity events, or incidence of crime events. Point pattern models can attempt to explai ...
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Journal ArticleStatistica Sinica · January 2019
Species distribution models usually attempt to explain presence-absence or abundance of a species at a site in terms of the environmental features (so-called abiotic features) present at the site. Historically, such models have considered species individua ...
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Journal ArticleTest · December 1, 2018
Learning about the behavior of land surface gradients and, in particular, slope and aspect over a region from a dataset of levels obtained at a set of (possibly) irregularly spaced locations assumes importance in a variety of applications. A primary exampl ...
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Journal ArticleEnvironmetrics · November 1, 2018
Rigorous and rapid assessment of ambient ozone exposure is important for informing the public about ozone levels that may lead to adverse health effects. In this paper, we use hierarchical modeling to enable real-time forecasting of 8-hr average ozone expo ...
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Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · September 1, 2018
The distinction between an overlap in species daily activity patterns and proximate co-occurrence of species for a location and time due to behavioral attraction or avoidance is critical when addressing the question of species co-occurrence. We use data fr ...
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ConferenceIEEE Transactions on Information Theory · March 1, 2018
We study the maximum weight matching (MWM) problem for general graphs through the max-product belief propagation (BP) and related Linear Programming (LP). The BP approach provides distributed heuristics for finding the maximum a posteriori (MAP) assignment ...
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Journal ArticleMethods in Ecology and Evolution · March 1, 2018
Understanding and predicting how species traits are shaped by prevailing environmental conditions is an important yet challenging task in ecology. Functional trait-based approaches can replace potentially idiosyncratic species-specific response models in l ...
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Journal ArticleStochastic environmental research and risk assessment : research journal · February 2018
It is often of interest to model the incidence and duration of threshold exceedance events for an environmental variable over a set of monitoring locations. Such data arrive over continuous time and can be considered as observations of a two-state process ...
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ConferenceSpringer Proceedings in Mathematics and Statistics · January 1, 2018
In recent years, state of the art brain imaging techniques like Functional Magnetic Resonance Imaging (fMRI), have raised new challenges to the statistical community, which is asked to provide new frameworks for modeling and data analysis. Here, motivated ...
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Journal ArticleStatistics in medicine · December 2017
In health exposure modeling, in particular, disease mapping, the ecological fallacy arises because the relationship between aggregated disease incidence on areal units and average exposure on those units differs from the relationship between the event of i ...
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Journal ArticleSpatial Statistics · August 1, 2017
Customarily, for housing markets, interest focuses on selling prices of properties at locations and times. Hedonic models are employed using property-level, neighborhood-level, and economic regressors. However, in hedonic modeling the fact that the locatio ...
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Journal ArticleJournal of Computational and Graphical Statistics · July 3, 2017
In many applications involving spatial point patterns, we find evidence of inhibition or repulsion. The most commonly used class of models for such settings are the Gibbs point processes. A recent alternative, at least to the statistical community, is the ...
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Journal ArticleAnnals of Applied Statistics · June 1, 2017
We view the locations and times of a collection of crime events as a space–time point pattern. Then, with either a nonhomogeneous Poisson process or with a more general Cox process, we need to specify a space–time intensity. For the latter, we need a rando ...
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Journal ArticleAnnual review of statistics and its application · March 2017
The most prevalent spatial data setting is, arguably, that of so-called geostatistical data, data that arise as random variables observed at fixed spatial locations. Collection of such data in space and in time has grown enormously in the past two decades. ...
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Journal ArticleAnnals of Applied Statistics · March 1, 2017
Prediction of aboveground biomass, particularly at large spatial scales, is necessary for estimating global-scale carbon sequestration. Since biomass can be measured only by sacrificing trees, total biomass on plots is never observed. Rather, allometric eq ...
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Journal ArticleStochastic Environmental Research and Risk Assessment · January 1, 2017
Recently, there has been increased interest in the behavior of wildfires. Behavior includes explaining: incidence of wildfires; recurrence times for wildfires; sizes, scars, and directions of wildfires; and recovery of burned regions after a wildfire. We s ...
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Journal ArticleBayesian Analysis · January 1, 2017
Spatial point pattern data describes locations of events observed over a given domain, with the number of and locations of these events being random. Historically, data analysis for spatial point patterns has focused on rejecting complete spatial randomnes ...
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Journal ArticleBayesian Analysis · January 1, 2017
Species distribution models are used to evaluate the variables that affect the distribution and abundance of species and to predict biodiversity. Historically, such models have been fitted to each species independently. While independent models can provide ...
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Journal ArticleStochastic Environmental Research and Risk Assessment · December 1, 2016
We consider modeling of angular or directional data viewed as a linear variable wrapped onto a unit circle. In particular, we focus on the spatio-temporal context, motivated by a collection of wave directions obtained as computer model output developed dyn ...
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Journal ArticleSpatial Statistics · November 1, 2016
Spatial analysis has grown at a remarkable rate over the past two decades. Fueled by sophisticated GIS software and inexpensive and fast computation, collection of data with spatially referenced information has increased. Recognizing that such information ...
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Journal ArticleWiley interdisciplinary reviews. Computational statistics · September 2016
Gaussian Process (GP) models provide a very flexible nonparametric approach to modeling location-and-time indexed datasets. However, the storage and computational requirements for GP models are infeasible for large spatial datasets. Nearest Neighbor Gaussi ...
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Journal ArticleTest · June 1, 2016
Circular data arise in many areas of application. Recently, there has been interest in looking at circular data collected separately over time and over space. Here, we extend some of this work to the spatio-temporal setting, introducing space–time dependen ...
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Journal ArticleJournal of the American Statistical Association · April 2, 2016
Spatial process models for analyzing geostatistical data entail computations that become prohibitive as the number of spatial locations become large. This article develops a class of highly scalable nearest-neighbor Gaussian process (NNGP) models to provid ...
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Journal ArticleEnvironmental and Ecological Statistics · March 1, 2016
Predictions of above-ground biomass and the change in above-ground biomass require attachment of uncertainty due the range of reported predictions for forests. Because above-ground biomass is seldom measured, there have been no opportunities to obtain such ...
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Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · March 1, 2016
Typical ecological gradient analysis for plant species considers variation in the response along a gradient of covariate values, for example, temperature or precipitation. Response is customarily modeled through the presence/absence or a suitable measure o ...
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ConferenceWSDM 2016 - Proceedings of the 9th ACM International Conference on Web Search and Data Mining · February 8, 2016
Discovering latent structures in spatial data is of critical importance to understanding the user behavior of locationbased services. In this paper, we study the problem of geographic segmentation of spatial data, which involves dividing a collection of ob ...
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Journal ArticleJournal of Statistical Planning and Inference · January 1, 2016
This paper develops methodology for local sensitivity analysis based on directional derivatives associated with spatial processes. Formal gradient analysis for spatial processes was elaborated in previous papers, focusing on distribution theory for directi ...
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Conference33rd International Conference on Machine Learning, ICML 2016 · January 1, 2016
We develop continuous-time probabilistic models to study trajectory data consisting of times and locations of user 'check-ins'. We model the data as realizations of a marked point process, with intensity and mark-distribution modulated by a latent Markov j ...
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Journal ArticleEnvironmetrics · December 1, 2015
PM2.5 exposure is linked to a number of adverse health effects such as lung cancer and cardiovascular disease. However, PM2.5 is a complex mixture of different species whose composition varies substantially in both space and time. An open question is how t ...
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Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · September 23, 2015
The velocity of climate change is defined as an instantaneous rate of change needed to maintain a constant climate. It is developed as the ratio of the temporal gradient of climate change over the spatial gradient of climate change. Ecologically, understan ...
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Journal ArticleWiley Interdisciplinary Reviews: Computational Statistics · September 1, 2015
In spatial analysis, typically we specify a region of interest and consider a spatial surface over the region. It is often of interest to ascertain where the surface is changing rapidly. Identifying locations or curves where there is rapid change is referr ...
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Journal ArticleJournal of Geographical Systems · July 1, 2015
Typical ecological gradient analyses consider variation in the response of plants along a gradient of covariate values, but generally constrain themselves to predetermined response curves and ignore spatial autocorrelation. In this paper, we develop a form ...
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Journal ArticleSpatial Statistics · May 1, 2015
Computer models are often deterministic simulators used to predict several environmental phenomena. Such models do not associate any measure of uncertainty with their output since they are derived from deterministic specifications. However, many sources of ...
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Journal ArticleJournal of Statistical Software · January 1, 2015
In this paper we detail the reformulation and rewrite of core functions in the spBayes R package. These efforts have focused on improving computational efficiency, flexibility, and usability for point-referenced data models. Attention is given to algorithm ...
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Journal ArticleStatistica Sinica · January 1, 2015
It is valuable to have a better understanding of factors that influence sea motion and to provide more accurate forecasts. In particular, we are motivated by data on wave heights and outgoing wave directions over a region in the Adriatic sea during the tim ...
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Journal ArticleEnvironmetrics · December 1, 2014
Tree growth estimation is a challenging task as difficulties associated with data collection and inference often result in inaccurate estimates. Two main methods for tree growth estimation are diameter tape measurements and increment cores. The former invo ...
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Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · December 1, 2014
We address the question of identifying the relative importance of covariates for model response, a form of sensitivity analysis. Relative importance is typically implemented as part of the model building procedure, e.g., forward variable selection or backw ...
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Journal ArticleJournal of the Royal Statistical Society. Series C, Applied statistics · November 2014
Researchers in the health and social sciences often wish to examine joint spatial patterns for two or more related outcomes. Examples include infant birth weight and gestational length, psychosocial and behavioral indices, and educational test scores from ...
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Journal ArticleJournal of the American Statistical Association · October 2, 2014
Directional data naturally arise in many scientific fields, such as oceanography (wave direction), meteorology (wind direction), and biology (animal movement direction). Our contribution is to develop a fully model-based approach to capture structured spat ...
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Journal ArticleJournal of Statistical Theory and Practice · July 3, 2014
Our interest is in analyzing fire regimes in the Mediterranean ecosystem in the Cape Floristic Region of South Africa (CFR). With this objective, we consider an extensive database of observed fires with high-resolution meteorological data during the period ...
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Journal ArticleEcological applications : a publication of the Ecological Society of America · July 2014
The perceived threat of climate change is often evaluated from species distribution models that are fitted to many species independently and then added together. This approach ignores the fact that species are jointly distributed and limit one another. Spe ...
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Journal ArticleStatistics in medicine · May 2014
Data that include fine geographic information, such as census tract or street block identifiers, can be difficult to release as public use files. Fine geography provides information that ill-intentioned data users can use to identify individuals. We propos ...
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Journal ArticleGlobal change biology · April 2014
Understanding the drivers of phenological events is vital for forecasting species' responses to climate change. We developed flexible Bayesian survival regression models to assess a 29-year, individual-level time series of flowering phenology from four tax ...
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Journal ArticleEnvironmetrics · January 1, 2014
The US Environmental Protection Agency is required to monitor, regulate, and set national ambient air quality standards for ozone. To investigate ozone exposure, the Environmental Protection Agency utilizes monitoring devices along with estimates of gridde ...
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Journal ArticleAnnals of the Institute of Statistical Mathematics · January 1, 2014
Analysis of variance is a standard statistical modeling approach for comparing populations. The functional analysis setting envisions that mean functions are associated with the populations, customarily modeled using basis representations, and seeks to com ...
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Journal ArticleGlobal change biology · January 2014
Tree species are predicted to track future climate by shifting their geographic distributions, but climate-mediated migrations are not apparent in a recent continental-scale analysis. To better understand the mechanisms of a possible migration lag, we anal ...
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Journal ArticleStatistical Methodology · January 1, 2014
The quantity of water contained in soil is referred to as the soil moisture. Soil moisture plays an important role in agriculture, percolation, and soil chemistry. Precipitation, temperature, atmospheric demand and topography are the primary processes that ...
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ConferenceIEEE International Symposium on Information Theory - Proceedings · December 19, 2013
Belief Propagation (BP) is a popular, distributed heuristic for performing MAP computations in Graphical Models. BP can be interpreted, from a variational perspective, as minimizing the Bethe Free Energy (BFE). BP can also be used to solve a special class ...
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Journal ArticleStatistical Science · November 1, 2013
Historically, matrix projection models (MPMs) have been employed to study population dynamics with regard to size, age or structure. To work with continuous traits, in the past decade, integral projection models (IPMs) have been proposed. Following the pat ...
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Journal ArticleStatistical Methodology · November 1, 2013
A common data analysis setting consists of a collection of datasets of varying sizes that are all relevant to a particular scientific question, but which include different subsets of the relevant variables, presumably with some overlap. Here, we demonstrat ...
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Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · September 1, 2013
Compositional data analysis considers vectors of nonnegative-valued variables subject to a unit-sum constraint. Our interest lies in spatial compositional data, in particular, land use/land cover (LULC) data in the northeastern United States. Here, the obs ...
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Journal ArticleEnvironmetrics · August 1, 2013
First flowering events in cherry trees are believed to be closely related to temperature patterns during the winter and spring months. Earlier works have incorporated the idea of temperature thresholds, defining chill and heat functions based on these thre ...
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Journal ArticleStatistical methodology · July 2013
The projected normal distribution is an under-utilized model for explaining directional data. In particular, the general version provides flexibility, e.g., asymmetry and possible bimodality along with convenient regression specification. Here, we clarify ...
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Journal ArticleSpatial statistics · May 2013
The accurate assessment of exposure to ambient ozone concentrations is important for informing the public and pollution monitoring agencies about ozone levels that may lead to adverse health effects. High-resolution air quality information can offer signif ...
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Journal ArticleComputational Statistics and Data Analysis · February 1, 2013
As a result of increased mobility patterns of workers, explaining labor flows and partitioning regions into local labor markets (LLMs) have become important economic issues. For the former, it is useful to understand jointly where individuals live and wher ...
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Journal ArticleLandscape Ecology · January 1, 2013
Woody invasive plants are an increasing component of the New England flora. Their success and geographic spread are mediated in part by landscape characteristics. We tested whether woody invasive plant richness was higher in landscapes with many forest edg ...
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ConferenceAdvances in Neural Information Processing Systems · January 1, 2013
Max-product 'belief propagation' (BP) is a popular distributed heuristic for finding the Maximum A Posteriori (MAP) assignment in a joint probability distribution represented by a Graphical Model (GM). It was recently shown that BP converges to the correct ...
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ConferenceJournal of Physics: Conference Series · January 1, 2013
This manuscript discusses computation of the Partition Function (PF) and the Minimum Weight Perfect Matching (MWPM) on arbitrary, non-bipartite graphs. We present two novel problem formulations-one for computing the PF of a Perfect Matching (PM) and one fo ...
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Chapter · January 1, 2013
We propose a class of misaligned data models for addressing typical small area estimation (SAE) problems. In particular, we extend hierarchical Bayesian atom-based models for spatial misalignment to the SAE context enabling use of auxiliary covariates, whi ...
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ConferenceUncertainty in Artificial Intelligence - Proceedings of the 28th Conference, UAI 2012 · December 1, 2012
This paper provides some new guidance in the construction of region graphs for Generalized Belief Propagation (GBP). We connect the problem of choosing the outer regions of a Loop- Structured Region Graph (SRG) to that of finding a fundamental cycle basis ...
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ConferenceUncertainty in Artificial Intelligence - Proceedings of the 28th Conference, UAI 2012 · December 1, 2012
We introduce a new cluster-cumulant expansion (CCE) based on the fixed points of iterative belief propagation (IBP). This expansion is similar in spirit to the loop-series (LS) recently introduced in [1]. However, in contrast to the latter, the CCE enjoys ...
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Journal ArticleJournal of agricultural, biological, and environmental statistics · December 2012
Population dynamics with regard to evolution of traits has typically been studied using matrix projection models (MPMs). Recently, to work with continuous traits, integral projection models (IPMs) have been proposed. Imitating the path with MPMs, IPMs are ...
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Journal ArticleSpatial statistics · December 2012
In applications where covariates and responses are observed across space and time, a common goal is to quantify the effect of a change in the covariates on the response while adequately accounting for the spatio-temporal structure of the observations. The ...
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Journal ArticleEnvironmetrics · November 2012
The choice of the sampling locations in a spatial network is often guided by practical demands. In particular, many locations are preferentially chosen to capture high values of a response, for example, air pollution levels in environmental monitoring. The ...
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Chapter · October 11, 2012
This chapter addresses the settings where there is need to specify knots in order to fit desired spatial models. That is, it seeks to fit hierarchical models in order to enable full inference and to adequately capture uncertainty. The chapter adopts an app ...
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Journal ArticleBiometrics · September 2012
Many applications involve count data from a process that yields an excess number of zeros. Zero-inflated count models, in particular, zero-inflated Poisson (ZIP) and zero-inflated negative binomial (ZINB) models, along with Poisson hurdle models, are commo ...
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Journal ArticleBiometrics · September 2012
We provide methods that can be used to obtain more accurate environmental exposure assessment. In particular, we propose two modeling approaches to combine monitoring data at point level with numerical model output at grid cell level, yielding improved pre ...
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Journal ArticleStatistical Modelling · June 1, 2012
We consider the setting of a multi-way contingency table with ordinal classifications. The contribution of this paper is to propose a joint probability model for the uncensored variables that is apart from the imposed categorization. Specifically, for an m ...
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Journal ArticleSpatial statistics · May 2012
This short paper is centered on hierarchical modeling for problems in spatial and spatio-temporal statistics. It draws its motivation from the interdisciplinary research work of the author in terms of applications in the environmental sciences - ecological ...
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Journal ArticleJ Epidemiol Community Health · February 2012
BACKGROUND: Studies examining the influence of maternal age and birth order on birthweight have not effectively disentangled the relative contributions of each factor to birthweight, especially as they may differ by race. METHODS: A population-based, cross ...
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Journal ArticleAnnals of Applied Statistics · January 1, 2012
Directional data arise in various contexts such as oceanography (wave directions) and meteorology (wind directions), as well as with measurements on a periodic scale (weekdays, hours, etc.). Our contribution is to introduce a model-based approach to handle ...
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Journal ArticleStatistical Methodology · January 1, 2012
Deterministic spatial interpolation algorithms such as the natural neighbor interpolation (NNI) or the Cressman interpolation schemes are widely used to interpolate environmental features. In particular, the former have been applied to digital elevation mo ...
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Journal ArticleJournal of Geographical Systems · January 1, 2012
In this paper, we extend the applicability of a previously proposed class of dynamic space-time models by enabling them to accommodate large datasets. We focus on the common setting where space is viewed as continuous but time is taken to be discrete. Scal ...
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ConferenceProceedings of the IEEE International Conference on Computer Vision · December 1, 2011
We present a new method to combine possibly inconsistent locally (piecewise) trained conditional models p(y αx α) into pseudo-samples from a global model. Our method does not require training of a CRF, but instead generates samples by iterating forward a w ...
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Journal ArticleEnvironmetrics · December 2011
Large point referenced datasets occur frequently in the environmental and natural sciences. Use of Bayesian hierarchical spatial models for analyzing these datasets is undermined by onerous computational burdens associated with parameter estimation. Low-ra ...
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ConferenceProceedings of the National Conference on Artificial Intelligence · November 2, 2011
We study iterative randomized greedy algorithms for generating (elimination) orderings with small induced width and state space size - two parameters known to bound the complexity of inference in graphical models. We propose and implement the Iterative Gre ...
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ConferenceProceedings of the National Conference on Artificial Intelligence · November 2, 2011
Many algorithms for performing inference in graphical models have complexity that is exponential in the treewidth - a parameter of the underlying graph structure. Computing the (minimal) treewidth is NP-complete, so stochastic algorithms are sometimes used ...
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Journal ArticleBrazilian Journal of Probability and Statistics · November 1, 2011
With wireless sensor networks, preserving battery life is critical. For such sensors, data collection is relatively cheap while data transmission is relatively expensive. For such networks in ecological settings, certain processes are sufficiently predicta ...
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Journal ArticleEcological applications : a publication of the Ecological Society of America · July 2011
Recent developments suggest that predictive modeling could begin to play a larger role not only for data analysis, but also for data collection. We address the example of efficient wireless sensor networks, where inferential ecosystem models can be used to ...
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Journal ArticleStatistics in medicine · July 2011
In environmental health studies air pollution measurements from the closest monitor are commonly used as a proxy for personal exposure. This technique assumes that air pollution concentrations are spatially homogeneous in the neighborhoods associated with ...
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Journal ArticleStatistica Sinica · July 1, 2011
We consider problems involving functional data where we have a collection of functions, each viewed as a process realization, e.g., a random curve or surface. For a particular process realization, we assume that the observation at a given location can be a ...
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Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · June 9, 2011
Traditional spatial linear regression models assume that the mean of the response is a linear combination of predictors measured at the same location as the response. In spatial applications, however, it seems plausible that neighboring predictors can also ...
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Journal ArticleEnvironmetrics · June 2011
In relating pollution to birth outcomes, maternal exposure has usually been described using monitoring data. Such characterization provides a misrepresentation of exposure as it (i) does not take into account the spatial misalignment between an individual' ...
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Journal ArticleEnvironmental science & technology · June 2011
To examine environmental and geologic determinants of arsenic in groundwater, detailed geologic data were integrated with well water arsenic concentration data and well construction data for 471 private wells in Orange County, NC, via a geographic informat ...
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Journal ArticleInternational Journal of Geographical Information Science · March 1, 2011
Ecologists often seek to understand patterns and processes across multiple spatial and temporal scales ranging from centimeters to hundreds of meters and from seconds to years. Hierarchical statistical models offer a framework for sampling design and analy ...
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Journal ArticleJournal of the Royal Statistical Society. Series C: Applied Statistics · January 1, 2011
Explaining the distribution of a species by using local environmental features is a long-standing ecological problem. Often, available data are collected as a set of presence locations only, thus precluding the possibility of a desired presence-absence ana ...
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ConferenceAdvances in Neural Information Processing Systems 23: 24th Annual Conference on Neural Information Processing Systems 2010, NIPS 2010 · December 1, 2010
The paper develops a connection between traditional perceptron algorithms and recently introduced herding algorithms. It is shown that both algorithms can be viewed as an application of the perceptron cycling theorem. This connection strengthens some herdi ...
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Journal ArticleThe annals of applied statistics · December 2010
Ozone and particulate matter PM(2.5) are co-pollutants that have long been associated with increased public health risks. Information on concentration levels for both pollutants come from two sources: monitoring sites and output from complex numerical mode ...
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Journal ArticleBayesian Analysis · December 1, 2010
We address the issue of inference for a noisy point pattern. The unobserved true point process is modelled as a nonhomogeneous Poisson process. For modeling the underlying intensity surface we use a scaled Gaussian mixture distribution. The noise that cree ...
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Journal ArticleAnnals of Applied Statistics · September 1, 2010
Modeling species abundance patterns using local environmental features is an important, current problem in ecology. The Cape Floristic Region (CFR) in South Africa is a global hot spot of diversity and endemism, and provides a rich class of species abundan ...
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Journal ArticleStatistics in medicine · July 2010
Birthweight and gestational age are closely related and represent important indicators of a healthy pregnancy. Customary modeling for birthweight is conditional on gestational age. However, joint modeling directly addresses the relationship between gestati ...
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Journal ArticleJournal of agricultural, biological, and environmental statistics · June 2010
Often, in environmental data collection, data arise from two sources: numerical models and monitoring networks. The first source provides predictions at the level of grid cells, while the second source gives measurements at points. The first is characteriz ...
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Journal ArticleJournal of the American Statistical Association · April 2010
We develop a model for stochastic processes with random marginal distributions. Our model relies on a stick-breaking construction for the marginal distribution of the process, and introduces dependence across locations by using a latent Gaussian copula mod ...
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Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · January 28, 2010
We propose a hierarchical modeling approach for explaining a collection of point-referenced extreme values. In particular, annual maxima over space and time are assumed to follow generalized extreme value (GEV) distributions, with parameters μ, σ, and ξ sp ...
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Journal ArticleEcological Modelling · January 10, 2010
In this study we combined an extensive database of observed wildfires with high-resolution meteorological data to build a novel spatially and temporally varying survival model to analyze fire regimes in the Mediterranean ecosystem in the Cape Floristic Reg ...
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ConferenceProceedings of the 26th Conference on Uncertainty in Artificial Intelligence, UAI 2010 · January 1, 2010
A major limitation of exact inference algorithms for probabilistic graphical models is their extensive memory usage, which often puts real-world problems out of their reach. In this paper we show how we can extend inference algorithms, particularly Bucket ...
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Journal ArticleJournal of the Royal Statistical Society. Series C, Applied statistics · January 2010
We consider joint spatial modelling of areal multivariate categorical data assuming a multiway contingency table for the variables, modelled by using a log-linear model, and connected across units by using spatial random effects. With no distinction regard ...
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Journal ArticlePublic Health Rep · 2010
OBJECTIVES: To better understand disparities in pregnancy outcomes, we analyzed data from North Carolina to determine how the pattern of maternal hypertensive disorders differs among non-Hispanic white (NHW), non-Hispanic black (NHB), and Hispanic women ac ...
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Journal ArticleStatistics and Computing · January 1, 2010
In this paper we present a fully model-based analysis of the effects of suppression and failure in data transmission with sensor networks. Sensor networks are becoming an increasingly common data collection mechanism in a variety of fields. Sensors can be ...
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Journal ArticleJournal of the Royal Statistical Society. Series C: Applied Statistics · January 1, 2010
Motivated by the problem of predicting chemical deposition in eastern USA at weekly, seasonal and annual scales, the paper develops a framework for joint modelling of point- and grid-referenced spatiotemporal data in this context. The hierarchical model pr ...
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Journal ArticleBayesian Analysis · December 1, 2009
This paper demonstrates the use and value of stochastic differential equations for modeling space-time data in two common settings. The first consists of point-referenced or geostatistical data where observations are collected at fixed locations and times. ...
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Conference2009 12th International Conference on Information Fusion, FUSION 2009 · November 18, 2009
An approach for evaluating the performance of decentralized estimation systems under non-ideal communi-cations is presented. Recent studies have shown that trans-mission disruptions occur frequently in tactical wireless net-works due to a variety of unpred ...
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Journal ArticleJournal of the Royal Statistical Society. Series B: Statistical Methodology · September 1, 2009
In functional data analysis, curves or surfaces are observed, up to measurement error, at a finite set of locations, for, say, a sample of n individuals. Often, the curves are homogeneous, except perhaps for individual-specific regions that provide heterog ...
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Journal ArticleComputational statistics & data analysis · June 2009
Advances in Geographical Information Systems (GIS) and Global Positioning Systems (GPS) enable accurate geocoding of locations where scientific data are collected. This has encouraged collection of large spatial datasets in many fields and has generated co ...
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Journal ArticleBiometrika · January 2009
In many modern experimental settings, observations are obtained in the form of functions, and interest focuses on inferences on a collection of such functions. We propose a hierarchical model that allows us to simultaneously estimate multiple curves nonpar ...
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Journal ArticleEnvironmental and Ecological Statistics · January 1, 2009
We propose a hierarchical modeling approach for explaining a collection of spatially referenced time series of extreme values. We assume that the observations follow generalized extreme value (GEV) distributions whose locations and scales are jointly spati ...
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Journal ArticleAnnals of Applied Statistics · December 1, 2008
Self-organizing maps (SOMs) are a technique that has been used with high-dimensional data vectors to develop an archetypal set of states (nodes) that span, in some sense, the high-dimensional space. Noteworthy applications include weather states as describ ...
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Journal ArticleThe annals of applied statistics · October 2008
Colon and rectum cancer share many risk factors, and are often tabulated together as "colorectal cancer" in published summaries. However, recent work indicating that exercise, diet, and family history may have differential impacts on the two cancers encour ...
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Journal ArticleJournal of the Royal Statistical Society. Series B, Statistical methodology · September 2008
With scientific data available at geocoded locations, investigators are increasingly turning to spatial process models for carrying out statistical inference. Over the last decade, hierarchical models implemented through Markov chain Monte Carlo methods ha ...
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ConferenceProceedings of SPIE - The International Society for Optical Engineering · June 5, 2008
The US Military has been undergoing a radical transition from a traditional "platform-centric" force to one capable of performing in a "Network-Centric" environment. This transformation will place all of the data needed to efficiently meet tactical and str ...
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Journal ArticleStatistics in medicine · May 2008
Sensitivity and specificity are two customary performance measures associated with medical diagnostic tests. Typically, they are modeled independently as a function of risk factors using logistic regression, which provides estimated functions for these pro ...
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Journal ArticleJournal of the Royal Statistical Society. Series C, Applied statistics · April 2008
This paper provides a space-time process model for total wet mercury deposition. Key methodological features introduced include direct modeling of deposition rather than of expected deposition, the utilization of precipitation information (there is no depo ...
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Journal ArticleBiometrical journal. Biometrische Zeitschrift · February 2008
Disease incidence or mortality data are typically available as rates or counts for specified regions, collected over time. We propose Bayesian nonparametric spatial modeling approaches to analyze such data. We develop a hierarchical specification using spa ...
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Journal ArticleJournal of the American Statistical Association · January 1, 2008
In multicenter studies, subjects in different centers may have different outcome distributions. This article is motivated by the problem of nonparametric modeling of these distributions, borrowing information across centers while also allowing centers to b ...
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ConferenceFUSION 2007 - 2007 10th International Conference on Information Fusion · December 1, 2007
The construction of belief networks is a widely used methodology for high level fusion modeling. While some of the components of a belief network deal with ambiguous (probabilistic) data, others may deal with vague (possibilistic) data. Given the need to r ...
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Journal ArticleBiometrika · December 1, 2007
Many models for the study of point-referenced data explicitly introduce spatial random effects to capture residual spatial association. These spatial effects are customarily modelled as a zero-mean stationary Gaussian process. The spatial Dirichlet process ...
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ConferenceCIDR 2007 - 3rd Biennial Conference on Innovative Data Systems Research · December 1, 2007
Wireless sensor networks are poised to enable continuous data collection on unprecedented scales, in terms of area location and size, and frequency. This is a great boon to fields such as ecological modeling. We are collaborating with researchers to build ...
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ConferenceProceedings of SPIE - The International Society for Optical Engineering · November 15, 2007
One of the greatest challenges in modern combat is maintaining a high level of timely Situational Awareness (SA). In many situations, computational complexity and accuracy considerations make the development and deployment of real-time, high-level inferenc ...
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Journal ArticleEnvironmental and Ecological Statistics · September 1, 2007
Estimation of population size has traditionally been viewed from a finite population sampling perspective. Typically, the objective is to obtain an estimate of the total population count of individuals within some region. Often, some stratification scheme ...
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Journal ArticleComputational Statistics and Data Analysis · April 1, 2007
Customary spatial modeling with point-referenced data introduces a modeling specification that includes a mean term, a spatial error or random effects term and a pure error term. The spatial random effects are usually modeled through a mean zero spatial pr ...
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Journal ArticleStatistics in medicine · March 2007
When interpreting screening mammograms radiologists decide whether suspicious abnormalities exist that warrant the recall of the patient for further testing. Previous work has found significant differences in interpretation among radiologists; their false- ...
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Journal ArticleMathematical Geology · February 1, 2007
Soil pollution data collection typically studies multivariate measurements at sampling locations, e.g., lead, zinc, copper or cadmium levels. With increased collection of such multivariate geostatistical spatial data, there arises the need for flexible exp ...
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Conference33rd International Conference on Very Large Data Bases, VLDB 2007 - Conference Proceedings · January 1, 2007
Sensor networks allow continuous data collection on unprecedented scales. The primary limiting factor of such networks is energy, of which communication is the dominant consumer. The default strategy of nodes continually reporting their data to the root re ...
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ConferenceLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) · January 1, 2007
Wireless sensor networks can be viewed as the integration of three subsystems: a low-impact in situ data acquisition and collection system, a system for inference of process models from observed data and a priori information, and a system that controls the ...
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Journal ArticleJournal of the American Statistical Association · January 2007
The assessment of air pollution regulatory programs designed to improve ground level ozone concentrations is a topic of considerable interest to environmental managers. To aid this assessment, it is necessary to model the space-time behavior of ozone for p ...
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Journal ArticleStatistics and computing · January 2007
This paper presents a methodology for model fitting and inference in the context of Bayesian models of the type f(Y | X, theta)f(X | theta)f(theta), where Y is the (set of) observed data, theta is a set of model parameters and X is an unobserved (latent) s ...
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Journal ArticleBayesian Analysis · December 1, 2006
Understanding spatial patterns of species diversity and the distributions of individual species is a consuming problem in biogeography and conservation. The Cape Floristic Region (CFR) of South Africa is a global hotspot of diversity and endemism, and the ...
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Journal ArticleJournal of the American Statistical Association · December 2006
Large-scale inference for random spatial surfaces over a region using spatial process models has been well studied. Under such models, local analysis of the surface (e.g., gradients at given points) has received recent attention. A more ambitious objective ...
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Journal ArticleStatistics in medicine · September 2006
Many biomedical data sets are concerned with relating the result of screening procedure(s) for a clinical event to the occurrence of that event. The effect of risk factors on measures of accuracy such as positive predictive value and negative predictive va ...
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Journal ArticleTrends in ecology & evolution · July 2006
Together, graphical models and the Bayesian paradigm provide powerful new tools that promise to change the way that environmental science is done. The capacity to merge theory with mechanistic understanding and empirical evidence, to assimilate diverse sou ...
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Journal ArticleEnvironmetrics · June 1, 2006
Environmental health research considers the relationship between exposures to environmental contaminants and particular health endpoints. Due to spatial structure associated with either exposures or outcomes, spatial modeling is making rapid inroads in env ...
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Journal ArticleMethodology and Computing in Applied Probability · June 1, 2006
When analyzing point-referenced spatial data, interest will be in the first order or global behavior of associated surfaces. However, in order to better understand these surfaces, we may also be interested in second order or local behavior, e.g., in the ra ...
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Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · March 1, 2006
Studies indicate that even short-term exposure to high concentrations of fine atmospheric particulate matter (PM2.5) can lead to long-term health effects. In this article, we propose a random effects model for PM2.5 concentrations. In particular, we antici ...
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Journal ArticleLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) · January 1, 2006
Next-generation wireless sensor networks may revolutionize understanding of environmental change by assimilating heterogeneous data, assessing the relative value and costs of data collection, and scheduling activities accordingly. Thus, they are dynamic, d ...
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Journal ArticleCanadian Journal of Statistics · January 1, 2006
The authors consider the issue of map positional error, or the difference between location as represented in a spatial database (i.e., a map) and the corresponding unobservable true location. They propose a fully model-based approach that incorporates aspe ...
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Journal ArticleStatistics in medicine · January 2006
Screening mammography is a widely used method for breast cancer detection. For each mammogram we propose a performance model based on order of outcomes. That is, we envision an initial assessment, a follow up assessment if the initial one is positive and, ...
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Journal ArticleJournal of Business and Economic Statistics · January 1, 2006
For point-referenced spatial data, we often create explanatory models that introduce regression structure with error consisting of a spatial term and a white noise term. Here we consider more flexible regression structures that allow spatially varying regr ...
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Journal ArticleJournal of the American Statistical Association · September 1, 2005
Customary modeling for continuous point-referenced data assumes a Gaussian process that is often taken to be stationary. When such models are fitted within a Bayesian framework, the unknown parameters of the process are assumed to be random, so a random Ga ...
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Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · September 1, 2005
A spatial cumulative distribution function (SCDF) gives the proportion of a spatial domain D having the value of some response variable less than a particular level w. This article provides a fully hierarchical approach to SCDF modeling, using a Bayesian f ...
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Journal ArticleEnvironmetrics · August 1, 2005
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 se ...
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Journal ArticleEcological Modelling · June 10, 2005
Establishing cause-effect relationships for deforestation at various scales has proven difficult even when rates of deforestation appear well documented. There is a need for better explanatory models, which also provide insight into the process of deforest ...
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Journal ArticleStatistical Science · May 1, 2005
When a candidate model for data is nonidentifiable, conventional wisdom dictates that the model must be simplified somehow so as to gain identifiability. We explore two scenarios involving mismeasured variables where, in fact, model expansion, as opposed t ...
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Journal ArticleJournal of Statistical Planning and Inference · March 1, 2005
There is by now a substantial literature on spatio-temporal modeling. However, to date, there exists essentially no literature which addresses the issue of process change from a certain time. In fact, if we look at change points for purely time series data ...
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Journal ArticleJournal of the Royal Statistical Society. Series C: Applied Statistics · February 8, 2005
Understanding spatial patterns of species diversity and the distributions of individual species is a consuming problem in biogeography and conservation. The Cape floristic region of South Africa is a global hot spot of diversity and endemism, and the Prote ...
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Journal ArticleStatistics and Computing · January 1, 2005
An auxiliary variable method based on a slice sampler is shown to provide an attractive simulation-based model fitting strategy for fitting Bayesian models under proper priors. Though broadly applicable, we illustrate in the context of fitting spatial mode ...
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Journal ArticleJournal of Real Estate Research · January 1, 2005
This paper provides a new model to explain local variation in apartment rents by introducing the notion of a spatial process. This model differs from those in the literature by explicitly specifying spatial association between pairs of locations as a funct ...
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Journal ArticleJournal of Business and Economic Statistics · April 1, 2004
Hedonic models are used almost universally for modeling house prices. Recognizing the importance of location, the past decade has seen increasing effort to introduce spatial considerations into such modeling. When spatial process models are used to capture ...
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Journal ArticleSouth African Journal of Science · January 1, 2004
Nearly a third of the area of South Africa's Cape Fioristic Region has been transformed by human land use and invasive alien plants. The vulnerability of remaining natural areas to transformation has been assessed, but less attention has been given to char ...
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Journal ArticleTest · January 1, 2004
Models for the analysis of multivariate spatial data are receiving increased attention these days. In many applications it will be preferable to work with multivariate spatial processes to specify such models. A critical specification in providing these mo ...
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Journal ArticleJournal of Geophysical Research: Atmospheres · December 27, 2003
Spatial data collection increasingly turns to vector valued measurements at spatial locations. An example is the observation of pollutant measurements. Typically, several different pollutants are observed at the same sampled location, referred to as a moni ...
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Journal ArticleJournal of the American Statistical Association · December 1, 2003
Spatial process models are now widely used for inference in many areas of application. In such contexts interest is often in the rate of change of a spatial surface at a given location in a given direction. Examples include temperature or rainfall gradient ...
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Journal ArticleEnvironmetrics · August 1, 2003
Recent work by the authors enabled a hierarchical modeling solution to the general change of support problem (COSP), where they seek to make inferences about the values of a variable at either points or regions different from those at which it has been obs ...
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Journal ArticleEnvironmental and Ecological Statistics · June 1, 2003
For modeling spatial processes, we propose a rich parametric class of stationary range anisotropic covariance structures that, when applied in R2, greatly increases the scope of variogram contors. Geometric anisotropy, which provides the most common genera ...
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Journal ArticleTheoretical population biology · May 2003
Using properties of moment stationarity we develop exact expressions for the mean and covariance of allele frequencies at a single locus for a set of populations subject to drift, mutation, and migration. Some general results can be obtained even for arbit ...
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Journal ArticleJournal of Statistical Planning and Inference · February 1, 2003
Model choice is a fundamental problem in data analysis. With interest in hierarchical models which typically arise as Bayesian specifications, we confine ourselves to Bayesian model choice criteria. If Y denotes the observed data and T(Y) is the criterion, ...
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Journal ArticleBiostatistics (Oxford, England) · January 2003
In the past decade conditional autoregressive modelling specifications have found considerable application for the analysis of spatial data. Nearly all of this work is done in the univariate case and employs an improper specification. Our contribution here ...
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Journal ArticleJournal of Applied Statistics · January 1, 2003
Bayesian hierarchical models are developed to estimate the frequencies of the alleles at the HLA-C locus in the presence of non-identifiable alleles and possible spatial correlations in a large but sparse, spatially defined database from Papua New Guinea. ...
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Journal ArticleJournal of Multivariate Analysis · January 1, 2003
For inferential analysis of spatial data, probability modelling in the form of a spatial stochastic process is often adopted. In the univariate case, a realization of the process is a surface over the region of interest. The specification of the process ha ...
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Journal ArticleScandinavian Journal of Statistics · January 1, 2003
With survival data there is often interest not only in the survival time distribution but also in the residual survival time distribution. In fact, regression models to explain residual survival time might be desired. Building upon recent work of Koftas & ...
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Journal ArticleCanadian Journal of Statistics · January 1, 2003
A multi-level model allows the possibility of marginalization across levels in different ways, yielding more than one possible marginal likelihood. Since log-likelihoods are often used in classical model comparison, the question to ask is which likelihood ...
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Journal ArticleEnvironmental and Ecological Statistics · December 1, 2002
Count data arises in many contexts. Here our concern is with spatial count data which exhibit an excessive number of zeros. Using the class of zero-inflated count models provides a flexible way to address this problem. Available covariate information sugge ...
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Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · September 1, 2002
Deforestation in the tropics has been a major concern in conservation science for more than two decades. A standard explanation is population pressure, argued through descriptive statistical summaries, but the connection between local population and forest ...
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Journal ArticleBiometrics · September 2002
In cytogenetic dosimetry, samples of cell cultures are exposed to a range of doses of a given agent. In each sample at each dose level, some measure of cell disability is recorded. The objective is to develop models that explain cell response to dose. Such ...
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Journal ArticleJournal of Computational and Graphical Statistics · August 26, 2002
Widely used parametric generalized linear models are, unfortunately, a somewhat limited class of specifications. Nonparametric aspects are often introduced to enrich this class, resulting in semiparametric models. Focusing on single or k-sample problems, m ...
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Journal ArticleInternational Journal of Phytoremediation · January 1, 2002
The capability of implementing a complete Bayesian analysis of experimental data has emerged over recent years due to computational advances developed within the statistical community. The objective of this paper is to provide a practical exposition of the ...
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Journal ArticleApplied Mathematical Finance · 2002
The capability of implementing a complete Bayesian analysis of
experimental data has emerged over recent years due to computational
advances developed within the statistical community. The objective of this
paper is to provide a practical exposition of ...
Cite
Journal ArticleReal Estate Economics · January 1, 2002
This article is motivated by the limited ability of standard hedonic price equations to deal with spatial variation in house prices. Spatial patterns of house prices can be viewed as the sum of many causal factors: Access to the central business district i ...
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Journal ArticleJournal of the American Statistical Association · December 1, 2001
Median regression models become an attractive alternative to mean regression models when employing flexible families of distributions for the errors. Classical approaches are typically algorithmic with desirable properties emerging asymptotically. However, ...
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Journal ArticleAnnals of the Institute of Statistical Mathematics · December 1, 2001
In comparing two populations, sometimes a model incorporating stochastic order is desired. Customarily, such modeling is done parametrically. The objective of this paper is to formulate nonparametric (possibly semiparametric) stochastic order specification ...
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Journal ArticleStatistica Sinica · October 1, 2001
Multilevel models incorporating random effects at the various levels are enjoying increased popularity. An implicit problem with such models is identifiability. From a Bayesian perspective, formal identifiability is not an issue. Rather, when implementing ...
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Chapter · January 1, 2001
The vignette series concludes with 22 contributions in Theory and Methods. It is, of course, impossible to cover all of theory and methods with so few articles, but we hope that a snapshot of what was, and what may be, is achieved. This is the essence of “ ...
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Journal ArticleJournal of the Royal Statistical Society. Series C: Applied Statistics · December 1, 2000
For a sample of 2361 patients admitted with suspected acute myocardial infarction to a set of 37 hospitals, recorded patient response variables include eligibility for treatment with aspirin, eligibility for treatment with thrombolytics, treatment with asp ...
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Journal ArticleJournal of the National Cancer Institute · October 2000
BackgroundThe cumulative risk of a false-positive mammogram can be substantial. We studied which variables affect the chance of a false-positive mammogram and estimated cumulative risks over nine sequential mammograms.MethodsWe used medic ...
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Journal ArticleJournal of Statistical Planning and Inference · September 1, 2000
The geostatistical spatial modelling framework envisions a random spatial process model Y(s) over a region S which is observed at spatial locations, say, s1,s2,...,sn. In the stationary Gaussian case, a mean function and a covariance function fully specify ...
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Journal ArticleJournal of the American Statistical Association · September 1, 2000
We consider inference using multivariate data that are spatially misaligned; that is, involving variables (typically counts or rates) that are aggregated over differing sets of regional boundaries. Geographic information systems enable the simultaneous dis ...
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Journal ArticleStatistics in Medicine · 2000
Screening examinations are widely utilized in detecting the presence of medical disorders, for instance, screening mammograms and clinical breast examinations for detection of breast cancer. Such procedures are invaluable in enabling early treatment but pr ...
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Journal ArticleJournal of the Royal Statistical Society. Series C: Applied Statistics · 2000
We propose a novel semiparametric version of the widely used proportional hazards survival model. Features include an arbitrarily rich class of continuous base-line hazards, an attractive epidemiological interpretation of the hazard as a latent competing r ...
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Journal ArticleJournal of the American Statistical Association · March 1, 1999
Markov chain Monte Carlo algorithms are widely used in the fitting of generalized linear models (GLMs). Such model fitting is somewhat of an art form, requiring suitable trickery and tuning to obtain results in which one can have confidence. A wide range o ...
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Journal ArticleMathematical Geology · January 1, 1999
A geometrically anisotropic spatial process can be viewed as being a linear transformation of an isotropic spatial process. Customary semivariogram estimation techniques often involve ed hoc selection of the linear transformation to reduce the region to is ...
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Journal ArticleBiometrics · September 1998
Unlike traditional approaches, Bayesian methods enable formal combination of expert opinion and objective information into interim and final analyses of clinical trial data. However, most previous Bayesian approaches have based the stopping decision on the ...
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Journal ArticleBiometrika · January 1, 1998
Model choice is a fundamental and much discussed activity in the analysis of datasets. Nonnested hierarchical models introducing random effects may not be handled by classical methods. Bayesian approaches using predictive distributions can be used though t ...
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Journal ArticleJournal of Business and Economic Statistics · January 1, 1998
This article focuses on the location, time, and spatio-temporal components associated with suitably aggregated data to improve prediction of individual asset values. Such effects are introduced in the context of hierarchical models, which we find more natu ...
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Journal ArticleReal Estate Economics · January 1, 1998
Real estate data are often characterized by data irregularities: missing data, censoring or truncation, measurement error, etc. Practitioners often discard missing-or censored-data cases and ignore measurement error. We argue here that an attractive remedy ...
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Journal ArticleTest · January 1, 1998
Recent computational advances have made it feasible to fit hierarchical models in a wide range of serious applications. In the process, the question of model adequacy arises. While model checking usually addresses the entire model specification, model fail ...
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Journal ArticleJournal of Statistical Planning and Inference · October 30, 1997
Generalized linear models have become a standard class of models for data analysts. However, in some applications, heterogeneity in samples is too great to be explained by the simple variance function implicit in such models. Utilizing a two parameter expo ...
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Journal ArticleJournal of the American Statistical Association · September 1, 1997
Biological size relationships (i.e., regression of one size variable on another) are typically monotone but often break down at extreme values of the variables. Here we study the way in which a plant's biomass is apportioned to reproductive and other life ...
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Journal ArticleJournal of the American Statistical Association · June 1, 1997
Although generalized linear models (GLM's) are an attractive and widely used class of models, they are limited in the range of density shapes that they can provide. For instance, they are unimodal exponential families of densities in the response variable ...
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Journal ArticleJournal of the American Statistical Association · June 1, 1997
Maps of regional morbidity and mortality rates are useful tools in determining spatial patterns of disease. Combined with sociodemographic census information, they also permit assessment of environmental justice; that is, whether certain subgroups suffer d ...
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Journal ArticleJournal of Agricultural, Biological, and Environmental Statistics · January 1, 1997
The variogram is a basic tool in geostatistics. In the case of an assumed isotropic process, it is used to compare variability of the difference between pairs of observations as a function of their distance. Customary approaches to variogram modeling creat ...
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Journal ArticleJournal of Statistical Planning and Inference · July 1, 1996
Regression models incorporating measurement error have received much attention in the recent literature. Measurement error can arise both in the explanatory variables and in the response. We introduce a fairly general model which permits both types of erro ...
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Journal ArticleBiometrika · September 1, 1995
SUMMARY: The generality and easy programmability of modern sampling-based methods for maximisation of likelihoods and summarisation of posterior distributions have led to a tremendous increase in the complexity and dimensionality of the statistical models ...
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Journal ArticleBiometrics · September 1995
We consider the usual proportional hazards model in the case where the baseline hazard, the covariate link, and the covariate coefficients are all unknown. Both the baseline hazard and the covariate link are monotone functions and thus are characterized us ...
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Journal ArticleJournal of the American Statistical Association · January 1, 1995
Expert opinion is often sought with regard to unknowns in a decision-making setting. For a univariate unknown, θ, our presumption is that such opinion is elicited as a partial probabilistic specification in the form of either probability assignments regard ...
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Journal ArticleBiometrika · June 1, 1994
SUMMARY: Generalized linear models are widely used by data analysis. However, the choice of the link function is often made arbitrarily. Here we permit the data to estimate the link function by incorporating it as an unknown in the model. Since the link fu ...
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Journal ArticleBiometrika · September 1, 1993
SUMMARY: In this paper we consider the analysis of record breaking data sets, where only observations that exceed, or only those that fall below, the current extreme value are recorded. Example application areas include industrial stress testing, meteorolo ...
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Journal ArticleCanadian Journal of Statistics · January 1, 1993
In statistical models involving constrained or missing data, likelihoods containing integrals emerge. In the case of both constrained and missing data, the result is a ratio of integrals, which for multivariate data may defy exact or approximate analytic e ...
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Journal ArticleFamily medicine · February 1992
Primary care researchers often wish to perform multiple variable analyses using variables measured at a nominal or ordinal level. This paper provides a step-by-step description of log-linear modeling, an approach uniquely well suited to explore and describ ...
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Journal ArticleJournal of the American Statistical Association · January 1, 1992
Constrained parameter problems arise in a wide variety of applications, including bioassay, actuarial graduation, ordinal categorical data, response surfaces, reliability development testing, and variance component models. Truncated data problems arise nat ...
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Journal ArticleStatistics and Computing · December 1, 1991
The Gibbs sampler has been proposed as a general method for Bayesian calculation in Gelfand and Smith (1990). However, the predominance of experience to date resides in applications assuming conjugacy where implementation is reasonably straightforward. Thi ...
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Journal ArticleStatistics and Computing · December 1, 1991
Improvements to the conventional ratio-of-uniforms method for random variate generation are proposed. A generalized radio-of-uniforms method is introduced, and it is demonstrated that relocation of the required density via the mode can greatly improve the ...
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Journal ArticleBiometrika · September 1, 1991
Summary: Previous attempts at implementing fully Bayesian nonparametric bioassay have enjoyed limited success due to computational difficulties. We show here how this problem may be generally handled using a sampling based approach to develop desired margi ...
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Journal ArticleCommunications in Statistics - Theory and Methods · January 1, 1991
In earlier work (Gelfand and Smith, 1990 and Gelfand et al, 1990) a sampling based approach using the Gibbs sampler was offered as a means for developing marginal posterior densities for a wide range of Bayesian problems several of which were previously in ...
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Journal ArticleBiometrika · December 1, 1990
The issue of creating overdispersion in a given one-parameter one-dimensional exponential family, by extending it to a two-parameter exponential family with the same support, is considered. An easily verifiable sufficient condition for this is derived. It ...
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Journal ArticleJournal of the American Statistical Association · January 1, 1990
Stochastic substitution, the Gibbs sampler, and the sampling-importance-resampling algorithm can be viewed as three alternative sampling- (or Monte Carlo-) based approaches to the calculation of numerical estimates of marginal probability distributions. Th ...
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Journal ArticleJournal of the American Statistical Association · January 1, 1990
The use of the Gibbs sampler as a method for calculating Bayesian marginal posterior and predictive densities is reviewed and illustrated with a range of normal data models, including variance components, unordered and ordered means, hierarchical growth cu ...
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Journal ArticleJournal of Multivariate Analysis · January 1, 1989
Suppose a random vector X has a multinormal distribution with covariance matrix Σ of the form Σ = Σi=1k θiMi, where Mi's form a known complete orthogonal set and θi's are the distinct unknown eigenvalues of Σ. The problem of estimation of Σ is considered u ...
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Journal ArticleJournal of Statistical Planning and Inference · January 1, 1988
The estimation of the ratio of two independent normal variances is considered under scale invariant squared error loss function, when the means are unknown. The best invariant estimator is shown to be inadmissible. Two new classes of improved estimators ar ...
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Journal ArticleJournal of Econometrics · January 1, 1988
In this paper we consider estimation of the disturbance variance in a linear regression model. A new class of improved estimators is obtained by extending results dating to Stein (1964). These estimators dominate the ordinary least squares estimator under ...
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Journal ArticleBulletin of Mathematical Biology · May 1, 1982
This paper characterizes the cycle structure of a completely random net. Variables such as number of cycles of a specified length, number of cycles, number of cyclic states and length of cycle are studied. A square array of indicator variables enables conv ...
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Journal ArticleBiological cybernetics · January 1982
Behavioral examination of binary switching net models has typically concerned itself with an examination of their cyclical character. This article considers two less frequently discussed behavioral variables--the density of "1"s in net states and the (Hamm ...
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Journal ArticleAustralian Journal of Statistics · January 1, 1981
For n independent Poisson processes such that the i th process has intensity function lMi(t) =δiρ(t; α) we consider estimation of p(t; α) =∫oρ:(u; α) du. Two procedures are developed, one using exact arrival times, the other using categorical arrival times ...
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Journal ArticleBehavioral Science · January 1, 1979
This paper makes two main points: (1) ensembles can be used in certain circumstances to represent the perspective of a manager facing a complex organization, and (2) some management strategies can be formalized as equivalence relations over control system ...
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Journal ArticleInternational Journal of General Systems · January 1, 1977
Systems which are built up from functionally identical elements having two inputs and two internal states are subjected to random initial positions and random structural connections such that a random determination of cycle length is achieved. This artific ...
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Journal ArticleNaval Research Logistics · January 1, 1976
The paper examines several types of procedures for attribute sampling inspection - the widely used Military Standard 105D plans, the lesser known Double Zero plans as developed by Ellis and the Narrow Limit gaging plans of Ott and Mundel. Each of the proce ...
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