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  1. No Access

    Chapter

    Topological Data Analysis for Directed Dependence Networks of Multivariate Time Series Data

    Topological data analysis (TDA) approaches are becoming increasingly popular for studying the dependence patterns in multivariate time series data. In particular, various dependence patterns in brain networks ...

    Anass El Yaagoubi, Hernando Ombao in Research Papers in Statistical Inference f… (2023)

  2. No Access

    Article

    Bayesian parameter inference for partially observed stochastic differential equations driven by fractional Brownian motion

    In this paper we consider Bayesian parameter inference for partially observed fractional Brownian motion models. The approach we follow is to time-discretize the hidden process and then to design Markov chain ...

    Mohamed Maama, Ajay Jasra, Hernando Ombao in Statistics and Computing (2022)

  3. No Access

    Article

    A Generalized Interrupted Time Series Model for Assessing Complex Health Care Interventions

    Assessing the impact of complex interventions on measurable health outcomes is a growing concern in health care and health policy. Interrupted time series (ITS) designs borrow from traditional case-crossover d...

    Maricela Cruz, Hernando Ombao, Daniel L. Gillen in Statistics in Biosciences (2022)

  4. Article

    Open Access

    Estimation and probabilistic projection of levels and trends in the sex ratio at birth in seven provinces of Nepal from 1980 to 2050: a Bayesian modeling approach

    The sex ratio at birth (SRB; ratio of male to female births) in Nepal has been reported around the normal level on the national level. However, the national SRB could mask the disparity within the country. Giv...

    Fengqing Chao, Samir KC, Hernando Ombao in BMC Public Health (2022)

  5. No Access

    Article

    Clustering Brain Signals: a Robust Approach Using Functional Data Ranking

    In this paper, we analyze electroencephalograms (EEGs) which are recordings of brain electrical activity. We develop new clustering methods for identifying synchronized brain regions, where the EEGs show simil...

    Tianbo Chen, Ying Sun, Carolina Euan, Hernando Ombao in Journal of Classification (2021)

  6. No Access

    Chapter and Conference Paper

    Lattice Paths for Persistent Diagrams

    Persistent homology has undergone significant development in recent years. However, one outstanding challenge is to build a coherent statistical inference procedure on persistent diagrams. In this paper, we fi...

    Moo K. Chung, Hernando Ombao in Interpretability of Machine Intelligence i… (2021)

  7. No Access

    Article

    Modeling dependence via copula of functionals of Fourier coefficients

    The goal of this paper is to develop a measure for characterizing complex dependence between time series that cannot be captured by traditional measures such as correlation and coherence. Our approach is to us...

    Charles Fontaine, Ron D. Frostig, Hernando Ombao in TEST (2020)

  8. No Access

    Article

    Modeling High-Dimensional Multichannel Brain Signals

    Our goal is to model and measure functional and effective (directional) connectivity in multichannel brain physiological signals (e.g., electroencephalograms, local field potentials). The difficulties from ana...

    Lechuan Hu, Norbert J. Fortin, Hernando Ombao in Statistics in Biosciences (2019)

  9. No Access

    Article

    Fisher information matrix of binary time series

    A common approach to analyzing categorical correlated time series data is to fit a generalized linear model (GLM) with past data as covariate inputs. There remain challenges to conducting inference for time se...

    Xu Gao, Daniel Gillen, Hernando Ombao in METRON (2018)

  10. No Access

    Article

    Modeling Binary Time Series Using Gaussian Processes with Application to Predicting Sleep States

    Motivated by the problem of predicting sleep states, we develop a mixed effects model for binary time series with a stochastic component represented by a Gaussian process. The fixed component captures the effe...

    Xu Gao, Babak Shahbaba, Hernando Ombao in Journal of Classification (2018)

  11. No Access

    Article

    The Hierarchical Spectral Merger Algorithm: A New Time Series Clustering Procedure

    We present a new method for time series clustering which we call the Hierarchical Spectral Merger (HSM) method. This procedure is based on the spectral theory of time series and identifies series that share si...

    Carolina Euán, Hernando Ombao, Joaquín Ortega in Journal of Classification (2018)

  12. Article

    Open Access

    Ensemble-based methods for forecasting census in hospital units

    The ability to accurately forecast census counts in hospital departments has considerable implications for hospital resource allocation. In recent years several different methods have been proposed forecasting...

    Devin C Koestler, Hernando Ombao, Jesse Bender in BMC Medical Research Methodology (2013)

  13. No Access

    Article

    Patterns of white matter injury in HIV infection after partial immune reconstitution: a DTI tract-based spatial statistics study

    HIV-infected individuals with severe immune suppression are more likely to develop HIV-associated neurocognitive disorders than those with preserved immune function. While partial immune reconstitution occurs ...

    Tong Zhu, Jianhui Zhong, Rui Hu, Madalina Tivarus, Sven Ekholm in Journal of NeuroVirology (2013)

  14. No Access

    Article

    Discussion: Time-threshold maps: Using information from wavelet reconstructions with all threshold values simultaneously

    Hernando Ombao in Journal of the Korean Statistical Society (2012)

  15. No Access

    Article

    Clinical contributors to cerebral white matter integrity in HIV-infected individuals

    HIV-infected people frequently exhibit brain dysfunction characterized by preferential damage to the cerebral white matter. Despite suppressed viral load and reconstituted immune function afforded by combinati...

    Assawin Gongvatana, Ronald A. Cohen, Stephen Correia in Journal of NeuroVirology (2011)

  16. No Access

    Chapter and Conference Paper

    Online Analysis of Seismic Signals

    Seismic signals can be modeled as non-stationary time series. Methods for analyzing non-stationary time series that have been recently developed are proposed in Adak [1], West, et al. [25] and Ombao, et al. [1...

    Hernando Ombao, Jungeon Heo, David Stoffer in Time Series Analysis and Applications to G… (2004)

  17. No Access

    Chapter and Conference Paper

    Online Analysis of Seismic Signals

    Seismic signals can be modeled as non-stationary time series. Methods for analyzing non-stationary time series that have been recently developed are proposed in Adak [1], West, et al. [25] and Ombao, et al. [1...

    Hernando Ombao, Jungeun Heo, David Stoffer in Time Series Analysis and Applications to G… (2004)

  18. No Access

    Article

    The SLEX Model of a Non-Stationary Random Process

    We propose a new model for non-stationary random processes to represent time series with a time-varying spectral structure. Our SLEX model can be considered as a discrete time-dependent Cramér spectral represe...

    Hernando Ombao, Jonathan Raz in Annals of the Institute of Statistical Mat… (2002)