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72 results on '"Ngatchou-Wandji, Joseph"'

51. Behavior of binned kernel density estimators for non-stationary random fields

Author

Ngatchou Wandji, Joseph, Harel, Michel, Lenain, Jean-François, Institut Élie Cartan de Lorraine (IECL), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Institut de Mathématiques de Toulouse UMR5219 (IMT), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Groupement de Recherche Eau, Sol, Environnement (GRESE), Université de Limoges (UNILIM), Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[STAT.AP]Statistics [stat]/Applications [stat.AP], [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], [STAT.TH]Statistics [stat]/Statistics Theory [stat.TH], [STAT.ME]Statistics [stat]/Methodology [stat.ME], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2015

54. On choosing a mixture model for clustering

Author

Ngatchou Wandji , Joseph, Bulla , Jan, Institut Élie Cartan de Lorraine (IECL), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Mathématiques Nicolas Oresme (LMNO), Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU), Probabilités et statistiques, Institut Élie Cartan de Lorraine ( IECL ), Université de Lorraine ( UL ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Lorraine ( UL ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire de Mathématiques Nicolas Oresme ( LMNO ), Université de Caen Normandie ( UNICAEN ), Normandie Université ( NU ) -Normandie Université ( NU ) -Centre National de la Recherche Scientifique ( CNRS ), Nutrition-Génétique et Exposition aux Risques Environnementaux (NGERE), Institut National de la Santé et de la Recherche Médicale (INSERM)-Université de Lorraine (UL), Département des sciences de l'information et biostatistiques, and École des Hautes Études en Santé Publique [EHESP] (EHESP)

Subjects
Statistics::Theory, [STAT.AP]Statistics [stat]/Applications [stat.AP], Statistics::Applications, 05 social sciences, [ STAT.AP ] Statistics [stat]/Applications [stat.AP], 06 humanities and the arts, [STAT.TH]Statistics [stat]/Statistics Theory [stat.TH], 0603 philosophy, ethics and religion, ICL, [ STAT.TH ] Statistics [stat]/Statistics Theory [stat.TH], Statistics::Computation, Statistics::Machine Learning, [ STAT.ME ] Statistics [stat]/Methodology [stat.ME], [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], AIC, 0502 economics and business, BIC, Statistics::Methodology, Mixtures models, 060301 applied ethics, [ MATH.MATH-ST ] Mathematics [math]/Statistics [math.ST], [STAT.ME]Statistics [stat]/Methodology [stat.ME], 050203 business & management, ComputingMilieux_MISCELLANEOUS, clustering
Abstract

Two methods for both clustering data and choosing a mixture model are proposed. First, the unknown clusters are assessed. Then, the likelihood conditional to these clusters is written as the product of likelihoods from each cluster. AIC and BIC type-approximations are then applied, and the resulting criteria turn out to be the sum of the AIC or BIC relative to each cluster. The performances of our methods are evaluated on real data examples and numerical simulations.

Published
2013

55. Recent Tests for Symmetry with Multivariate and Structured Data: A Review

Author

Meintanis, Simos, Ngatchou-Wandji, Joseph, Department of Economics, National and Kapodistrian University of Athens, National and Kapodistrian University of Athens (NKUA)-National and Kapodistrian University of Athens (NKUA), Institut Élie Cartan de Nancy (IECN), Institut National de Recherche en Informatique et en Automatique (Inria)-Université Henri Poincaré - Nancy 1 (UHP)-Université Nancy 2-Institut National Polytechnique de Lorraine (INPL)-Centre National de la Recherche Scientifique (CNRS), and National and Kapodistrian University of Athens (NKUA)

Subjects
[STAT]Statistics [stat], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2011
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56. Goodness-of-fit tests for multivariate stable distributions based on the empirical characteristic function

Author

21262977 - Meintanis, Simos George, Meintanis, Simos G., Ngatchou-Wandji, Joseph, Taufer, Emanuele, 21262977 - Meintanis, Simos George, Meintanis, Simos G., Ngatchou-Wandji, Joseph, and Taufer, Emanuele

Abstract

We consider goodness-of-fit testing for multivariate stable distributions. The proposed test statistics exploit a characterizing property of the characteristic function of these distributions and are consistent under some conditions. The asymptotic distribution is derived under the null hypothesis as well as under local alternatives. Conditions for an asymptotic null distribution free of parameters and for affine invariance are provided. Computational issues are discussed in detail and simulations show that with proper choice of the user parameters involved, the new tests lead to powerful omnibus procedures for the problem at hand

Published
2015

57. Sur les modèles de comptage à inflation de zéro avec application à la modélisation de la tendance dans la prévalence de certaines maladies allergiques liées au travail en France de 2001 à 2007

Author

Ngatchou-Wandji, Joseph, Paris, Christophe, Sfds-Hal, Conférence, Nutrition-Génétique et Exposition aux Risques Environnementaux (NGERE), Institut National de la Santé et de la Recherche Médicale (INSERM)-Université de Lorraine (UL), and Université de Lorraine (UL)-Institut National de la Santé et de la Recherche Médicale (INSERM)

Subjects
[MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], [STAT.TH] Statistics [stat]/Statistics Theory [stat.TH], [STAT.TH]Statistics [stat]/Statistics Theory [stat.TH], [MATH.MATH-ST] Mathematics [math]/Statistics [math.ST]
Abstract

International audience; Les modèles de comptage à inflation de zéro sont souvent utilisés pour modéliser des données de comptage surdispersées et/ou comportant une grande proportion de zéro. Ces modèles ont été utilisés avec succès en économetrie, en épidémiologie, en santé publique, en biologie et dans bien d'autres domaines. Dans cette note, nous faisons le survol de la littérature sur ces modèles, puis les appliquons à la modélisation de la tendance dans la prévalence de certaines maladies allergiques liées au travail telles que l'asthme, la rhinite et la dermite. Les données sont françaises, collectées de janvier 2001 à décembre 2007 par le Réseau National de Vigilence et de Prévention des Pathologies Professionnelles (RNV3P).

Published
2010

58. Asymptotic inference in poverty indices: an empirical processes approach.

Author

Seck, Cheikh Tidiane, Ngatchou-Wandji, Joseph, and Lô, Gane Samb

Subjects
EMPIRICAL research, MATHEMATICAL sequences, VECTOR analysis, PARETO principle, STATISTICAL models
Abstract

We derive an empirical poverty index containing most of those proposed in the literature. Then, we study its asymptotic behavior by using empirical processes theory. From the results obtained, we derive a Wald-type test for comparing a vector of theoretical poverty indices to a vector of reference indices. We study the test statistic under the null hypothesis of equality, fixed alternatives, and a sequence of local alternatives. A simulation experiment conducted shows that our test performs well for exponential and Pareto data. [ABSTRACT FROM AUTHOR]

Published
2017
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60. Bayesian Modelling of PWR Vessels Flaw Distributions

Author

Celeux, Gilles, Persoz, Matthieu, Ngatchou Wandji, Joseph, Perrot, François, Statistical Inference for Industry and Health (IS2), Inria Grenoble - Rhône-Alpes, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire de Biométrie et Biologie Evolutive - UMR 5558 (LBBE), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS), and INRIA

Subjects
WEIBULL DISTRIBUTION, MISSING DATA, LOG-NORMAL DISTRIBUTION, BAYESIAN INFERENCE, [INFO.INFO-OH]Computer Science [cs]/Other [cs.OH], FLAW SIZE, FLAW DENSITY, MARKOV CHAIN MONTE CARLO
Abstract

We present a full Bayesian method for estimating the density and size distribution of subclad-flaws in French Pressurized Water Reactor (PWR) vessels. This model takes into account in service inspection (ISI) data, a flaw size-dependent probability of detection function (different function types are possible) with a threshold of detection, and a flaw sizing error distribution (different distribution types are possible). It is identified through a Markov Chain Monte Carlo (MCMC) algorithm. The article includes discussion for choosing the prior distribution parameters and an illustrative application is presented highlighting its ability to provide good parameter estimates even when a small number of flaws is observed.

Published
1998

61. A Nonparametric Goodness-of-fit Test for a Class of Parametric Autoregressive Models

Author

Ngatchou Wandji, Joseph, Statistical Inference for Industry and Health (IS2), Inria Grenoble - Rhône-Alpes, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire de Biométrie et Biologie Evolutive - UMR 5558 (LBBE), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS), and INRIA

Subjects
NONPARAMETRIC METHODS, MIXING, [INFO.INFO-OH]Computer Science [cs]/Other [cs.OH], GOODNESS-OF-FIT TESTS, CONTIGUITY, AUTOREGRESSIVE MODELS, NONLINEAR MODELS
Abstract

We derive a nonparametric test for discriminating between generalized autoregressive models. This test is based on a suitably normalized sum of residuals. The null distribution and the power of the test under both fixed and a sequence of local alternatives are studied under mild stationarity and $\alpha$--mixing conditions. This procedure can be applied to testing linear models against nonlinear models or certain nonlinear models against others. Numerical simulations show that the proposed test is powerful against most of the alternatives considered.

Published
1996

68. On Choosing a Mixture Model for Clustering.

Author

Ngatchou-Wandji, Joseph and Bulla, Jan

Subjects
*MIXTURES, *ALGORITHMS, *APPROXIMATION theory, *ENTROPY (Information theory), *MONTE Carlo method, *DATA analysis, *PERFORMANCE evaluation, *MATHEMATICAL models
Abstract

Two methods for clustering data and choosing a mixture model are proposed. First, we derive a new classification algorithm based on the classification likelihood. Then, the likelihood conditional on these clusters is written as the product of likelihoods of each cluster, and AIC- respectively BIC-type approximations are applied. The resulting criteria turn out to be the sum of the AIC or BIC relative to each cluster plus an entropy term. The performance of our methods is evaluated by Monte-Carlo methods and on a real data set, showing in particular that the iterative estimation algorithm converges quickly in general, and thus the computational load is rather low [ABSTRACT FROM AUTHOR]

Published
2013

71. On a new goodness-of-fit test for the Rayleigh distribution based on a conditional expectation characterization

Author

Shawn Carl Liebenberg, Joseph Ngatchou-Wandji, J.S. Allison, Ngatchou Wandji, Joseph, 20396236 - Liebenberg, Shawn Carl, 11985682 - Allison, James Samuel, Institut Élie Cartan de Lorraine (IECL), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), North-West University [Potchefstroom] (NWU), École des Hautes Études en Santé Publique [EHESP] (EHESP), and Département Méthodes quantitatives en santé publique (METIS)

Subjects
Statistics and Probability, goodness-of-fit, Characterization, 0211 other engineering and technologies, Goodness-of-fit, 02 engineering and technology, Characterization (mathematics), Conditional expectation, 01 natural sciences, 010104 statistics & probability, Goodness of fit, [STAT.AP] Statistics [stat]/Applications [stat.AP], [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], Applied mathematics, Rayleigh distribution, 0101 mathematics, [MATH.MATH-ST] Mathematics [math]/Statistics [math.ST], ComputingMilieux_MISCELLANEOUS, Mathematics, [STAT.AP]Statistics [stat]/Applications [stat.AP], 021103 operations research, [STAT.ME] Statistics [stat]/Methodology [stat.ME], [STAT.TH] Statistics [stat]/Statistics Theory [stat.TH], [STAT.TH]Statistics [stat]/Statistics Theory [stat.TH], [STAT.ME]Statistics [stat]/Methodology [stat.ME]
Abstract

International audience; We propose and study new goodness-of-fit tests for the Rayleigh distribution based on a characterization involving a conditional expectation. The asymptotic properties of the tests are explored and the performance of the new tests are evaluated and compared to that of existing tests by means of a Monte Carlo study. It is found that the newly proposed tests perform satisfactory compared to the competitor tests.

Published
2019
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72. Testing for serial independence in vector autoregressive models

Author

J.S. Allison, Simos G. Meintanis, Joseph Ngatchou-Wandji, National and Kapodistrian University of Athens (NKUA), North-West University [Potchefstroom] (NWU), Institut Élie Cartan de Lorraine (IECL), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), École des Hautes Études en Santé Publique [EHESP] (EHESP), 11985682 – Allison, James Samuel, Ngatchou Wandji, Joseph, 11985682 - Allison, James Samuel, and 21262977 - Meintanis, Simos George

Subjects
Statistics and Probability, Serial independence, Empirical characteristic function, 01 natural sciences, 010104 statistics & probability, [STAT.AP] Statistics [stat]/Applications [stat.AP], [MATH.MATH-ST]Mathematics [math]/Statistics [math.ST], VAR models, 0502 economics and business, Applied mathematics, 0101 mathematics, [MATH.MATH-ST] Mathematics [math]/Statistics [math.ST], ComputingMilieux_MISCELLANEOUS, 050205 econometrics, Mathematics, [STAT.AP]Statistics [stat]/Applications [stat.AP], Serial dependence tests, [STAT.ME] Statistics [stat]/Methodology [stat.ME], [STAT.TH] Statistics [stat]/Statistics Theory [stat.TH], 05 social sciences, [STAT.TH]Statistics [stat]/Statistics Theory [stat.TH], Autoregressive model, Product (mathematics), Statistics, Probability and Uncertainty, [STAT.ME]Statistics [stat]/Methodology [stat.ME]
Abstract

International audience; We consider tests for serial independence of arbitrary finite order for the innovations in vector autoregressive models. The tests are expressed as L2-type criteria involving the difference of the joint empirical characteristic function and the product of corresponding marginals. Asymptotic as well as Monte-Carlo results are presented.

Published
2018
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