A Fuzzy ARTMAP Nonparametric Probability Estimator For Nonstationary Pattern Recognition Problem

An incremental, nonparametric probability estimation procedure using the fuzzy ARTMAP neural network is introduced. In slow-learning mode, fuzzy ARTMAP searches for patterns of data on which to build ever more accurate estimates. In max-nodes mode, the network initially learns a fixed number of categories, and weights are then adjusted gradually.

Two-stage sequential procedure for nonparametric regression estimation

In nonparametric statistics the functional form of the relationship between the response variable and its associated predictor variables is unspecified but it is assumed to be a smooth function. We develop a procedure for constructing a fixed width confidence interval for the predicted value at a specified point of the independent variable. The optimal sample size for constructing this interval is obtained using a two stage sequential procedure which relies on some asymptotic properties of the Nadaraya--Watson and local linear estimators. Finally, a large scale simulation study demonstrates the applicability of the developed procedure for small and moderate sample sizes. The procedure developed here should find wide applicability since many practical problems which arise in industry involve estimating an unknown function.

The use of nonparametric contrasts in one-way layouts and random block designs

Nonparametric simple-contrast estimates for one-way layouts based on Hodges-Lehmann estimators for two samples and confidence intervals for all contrasts involving only two treatments are found in the literature.Tests for such contrasts are performed from the distribution of the maximum of the rank sum between two treatments. For random block designs, simple contrast estimates based on Hodges-Lehmann estimators for one sample are presented. However, discussions concerning the significance levels of more complex contrast tests in nonparametric statistics are not well outlined.This work aims at presenting a methodology to obtain p-values for any contrast types based on the construction of the permutations required by each design model using a C-language program for each design type. For small samples, all possible treatment configurations are performed in order to obtain the desired p-value. For large samples, a fixed number of random configurations are used. The program prompts the input of contrast coefficients, but does not assume the existence or orthogonality among them.In orthogonal contrasts, the decomposition of the value of the suitable statistic for each case is performed and it is observed that the same procedure used in the parametric analysis of variance can be applied in the nonparametric case, that is, each of the orthogonal contrasts has a chi(2) distribution with one degree of freedom. Also, the similarities between the p-values obtained for nonparametric contrasts and those obtained through approximations suggested in the literature are discussed.

Application of Local Rank Tests for Nonparametric Regression

Let Y_i = f(x_i) + E_i\ (1\le i\le n) with given covariates x_1\lt x_2\lt \cdots\lt x_n , an unknown regression function f and independent random errors E_i with median zero. It is shown how to apply several linear rank test statistics simultaneously in order to test monotonicity of f in various regions and to identify its local extrema.

Bayesian nonparametric latent variable models

L’un des problèmes importants en apprentissage automatique est de déterminer la complexité du modèle à apprendre. Une trop grande complexité mène au surapprentissage, ce qui correspond à trouver des structures qui n’existent pas réellement dans les données, tandis qu’une trop faible complexité mène au sous-apprentissage, c’est-à-dire que l’expressivité du modèle est insuffisante pour capturer l’ensemble des structures présentes dans les données. Pour certains modèles probabilistes, la complexité du modèle se traduit par l’introduction d’une ou plusieurs variables cachées dont le rôle est d’expliquer le processus génératif des données. Il existe diverses approches permettant d’identifier le nombre approprié de variables cachées d’un modèle. Cette thèse s’intéresse aux méthodes Bayésiennes nonparamétriques permettant de déterminer le nombre de variables cachées à utiliser ainsi que leur dimensionnalité. La popularisation des statistiques Bayésiennes nonparamétriques au sein de la communauté de l’apprentissage automatique est assez récente. Leur principal attrait vient du fait qu’elles offrent des modèles hautement flexibles et dont la complexité s’ajuste proportionnellement à la quantité de données disponibles. Au cours des dernières années, la recherche sur les méthodes d’apprentissage Bayésiennes nonparamétriques a porté sur trois aspects principaux : la construction de nouveaux modèles, le développement d’algorithmes d’inférence et les applications. Cette thèse présente nos contributions à ces trois sujets de recherches dans le contexte d’apprentissage de modèles à variables cachées. Dans un premier temps, nous introduisons le Pitman-Yor process mixture of Gaussians, un modèle permettant l’apprentissage de mélanges infinis de Gaussiennes. Nous présentons aussi un algorithme d’inférence permettant de découvrir les composantes cachées du modèle que nous évaluons sur deux applications concrètes de robotique. Nos résultats démontrent que l’approche proposée surpasse en performance et en flexibilité les approches classiques d’apprentissage. Dans un deuxième temps, nous proposons l’extended cascading Indian buffet process, un modèle servant de distribution de probabilité a priori sur l’espace des graphes dirigés acycliques. Dans le contexte de réseaux Bayésien, ce prior permet d’identifier à la fois la présence de variables cachées et la structure du réseau parmi celles-ci. Un algorithme d’inférence Monte Carlo par chaîne de Markov est utilisé pour l’évaluation sur des problèmes d’identification de structures et d’estimation de densités. Dans un dernier temps, nous proposons le Indian chefs process, un modèle plus général que l’extended cascading Indian buffet process servant à l’apprentissage de graphes et d’ordres. L’avantage du nouveau modèle est qu’il admet les connections entres les variables observables et qu’il prend en compte l’ordre des variables. Nous présentons un algorithme d’inférence Monte Carlo par chaîne de Markov avec saut réversible permettant l’apprentissage conjoint de graphes et d’ordres. L’évaluation est faite sur des problèmes d’estimations de densité et de test d’indépendance. Ce modèle est le premier modèle Bayésien nonparamétrique permettant d’apprendre des réseaux Bayésiens disposant d’une structure complètement arbitraire.

Statistical and scientometric analysis of international research in geographical and environmental education

Certain statistic and scientometric features of articles published in the journal “International Research in Geographical and Environmental Education” are examined in this paper, for the period 1992-2009, by applying nonparametric statistics and Shannon’s entropy (diversity) formula. The main findings of this analysis are: a) after 2004 the research priorities of researchers in geographical and environmental education seem to have changed, b) “teacher education” has been the most recurrent theme throughout these 18 years, followed by “values & attitudes” and “inquiry & problem solving” c) the themes “GIS” and “Sustainability” were the most “stable” throughout the 18 years, meaning that they maintained their ranks as publication priorities more than other themes, d) citations of IRGEE increase annually, e) the average thematic diversity of articles published during the period 1992-2009 is 82.7% of the maximum thematic diversity (very high), meaning that the Journal has the capacity to attract a wide readership for the 10 themes it has successfully covered throughout the 18 years of its publication.

Juvenile and small resident fishes of Florida Bay, a critical habitat in the Everglades National Park, Florida

This compendium presents information on the life history, diet, and abundance and distribution of 46 of the more abundant juvenile and small resident fish species, and data on three species of seagrasses in Florida Bay, Everglades National Park. Abundance and distribution of fish data were derived from three sampling schemes: (1) an otter trawl in basins (1984–1985, 1994–2001), (2) a surface trawl in basins (1984–1985), and (3) a surface trawl in channels (1984–1985). Results from surface trawling only included pelagic species. Collections made with an otter trawl in basins on a bi-monthly basis were emphasized. Nonparametric statistics were used to test spatial and temporal differences in the abundance of species and seagrasses. Fish species accounts were presented in four sections – Life history, Diet, Abundance and distribution, and Length-frequency distributions. Although Florida Bay is a subtropical estuary, the majority of fish species (76%) had warm-temperate affinities; i.e., only 24% were solely tropical species. The five most abundant species collected, in descending order, by (1) otter trawl in basins were: Eucinostomus gula, Lucania parva, Anchoa mitchilli, Lagodon rhomboides, and Syngnathus scovelli; (2) surface trawl in basins were: Hyporhamphus unifasciatus, Strongylura notata, Chriodorus atherinoides, Anchoa hepsetus, and Atherinomorus stipes; (3) surface trawl in channels were: Hypoatherina harringtonensis, A. stipes, A. mitchelli, H. unifasciatus, and C. atherinoides. (PDF file contains 219 pages.)

An ecological analysis of rockfish (Sebastes spp.) assemblages in the North Pacific Ocean along broad-scale environmental gradients

Environmental variability affects the distributions of most marine fish species. In this analysis, assemblages of rockfish (Sebastes spp.) species were defined on the basis of similarities in their distributions along environmental gradients. Data from 14 bottom trawl surveys of the Gulf of Alaska and Aleutian Islands (n=6767) were used. Five distinct assemblages of rockfish were defined by geographical position, depth, and temperature. The 180-m and 275-m depth contours were major divisions between assemblages inhabiting the shelf, shelf break, and lower continental slope. Another noticeable division was between species centered in southeastern Alaska and those found in the northern Gulf of Alaska and Aleutian Islands. The use of environmental variables to define the species composition of assemblages is different from the use of traditional methods based on clustering and nonparametric statistics and as such, environmentally based analyses should result in predictable assemblages of species that are useful for ecosystem-based management.

Comparison of Poaceae Pollen Counts Recorded at Sites in Portugal, Spain and the UK

The main aim of this study was to analyse the temporal and spatial variations in grass (Poaceae) pollen counts (2005–2011) recorded in Évora (Portugal), Badajoz (Spain) and Worcester (UK). Weekly average data were examined using nonparametric statistics to compare differences between places. On average, Évora recorded the earliest start dates of the Poaceae pollen seasons and Worcester the latest. The intensity of the Poaceae pollen season varied between sites, with Worcester usually recording the least and Évora the most grass pollen in a season. Mean durations of grass pollen seasons were 77 days in Évora, 78 days in Badajoz and 59 days in Worcester. Overall, longer Poaceae pollen seasons coincided with earlier pollen season start dates. Weekly pollen data, from March to September, from the three pollen-monitoring stations studied were compared. The best fit and most statistically significant correlations were obtained by moving Worcester data backward by 4 weeks (Évora, r = 0.810, p < 0.001) and 5 weeks (Badajoz,r = 0.849, p < 0.001). Weekly data from Worcester therefore followed a similar pattern to that of Badajoz and Évora but at a distance of more than 1,500 km and 4–5 weeks later. The sum of pollen recorded in a season was compared with monthly rainfall between January and May. The strongest positive relationship between season intensity and rainfall was between the annual sum of Poaceae pollen recorded in the season at Badajoz and Évora and total rainfall during January and February. Winter rainfall noticeably affects the intensity of Poaceae pollen seasons in Mediterranean areas, but this was not as important in Worcester.

Parámetros cuantitativos de la resonancia magnética cerebral en esclerosis múltiple y su correlación con la discapacidad

A pesar del amplio uso de la resonancia magnética en la esclerosis múltiple no se ha logrado una adecuada correlación clínico-imagenológica en esta enfermedad. Objetivo: Determinar la correlación del volumen normalizado de sustancia gris y del volumen de lesiones hipointensas en T1 obtenidos a partir de la resonancia magnética cerebral con la escala de discapacidad extendida en pacientes con diagnóstico de esclerosis múltiple. Materiales y métodos: Estudio retrospectivo en pacientes con diagnóstico de esclerosis múltiple de la Fundación Cardioinfantil. Se obtuvieron los resultados de la escala de discapacidad expandida así como análisis cuantitativo de las imágenes correspondientes de resonancia magnética por medio de la herramienta SIENA. Se cuantificaron el volumen del parénquima cerebral, sustancia gris, sustancia blanca y volumen de lesiones hipointensas en T1. Posteriormente, se relacionaron estos resultados con la escala de discapacidad extendida de Kurtzke previamente obtenida. Para el análisis estadístico se emplearon el test correlación de Spearman y t de Student y Hotelling. Resultados: Se incluyeron 58 pacientes, encontrándose correlaciones estadísticamente significativas entre la escala de discapacidad extendida y volumen de parénquima cerebral, volumen de sustancia gris y volumen de lesiones hipointensas en T1; de 0.384, 0.386 y 0.39. No se encontró una relación entre el volumen de sustancia blanca y la escala de discapacidad. Conclusiones: Existe una correlación clínico-imagenológica moderada en la esclerosis múltiple. La cuantificación de los parámetros propuestos en este estudio podría ser utilizada como herramienta en el seguimiento de la enfermedad y monitorización de nuevos tratamientos.

Comparación: injerto libre o cierre primario más lente de contacto, en resección de tumores de conjuntiva limbar

INTRODUCCION: Existe controversia en cuanto a la técnica quirúrgica para el manejo de tumores del limbo conjuntival. El uso de cierre primario con uso de lente de contacto puede ofrecer una mejor cicatrización y tener ventajas adicionales sobre la técnica tradicional con el uso de plastia. OBJETIVOS: Comparar los resultados en cuanto a grado de dolor, picadas, prurito, porcentaje de epitelización y cicatrización, comodidad del paciente, grado de quemosis y tiempo de retorno a actividades diarias en ambas técnicas quirúrgicas. MATERIALES Y METODOS: Experimento clínico controlado aleatorizado en dos grupos: Al primer grupo se le realizó cirugía de resección de la lesión más plastia. Al segundo grupo se le practicó la resección de la lesión cierre primario y lente de contacto. El seguimiento se realizó al primer y cuarto día, y cada semana durante el primer mes de postoperatorio. Se utilizó el SPSS 20.0 ® para análisis estadístico de datos y se utilizó estadística no paramétrica. RESULTADOS: Se conto con 10 pacientes por grupo. El dolor y porcentaje de cicatrización al primer día postoperatorio fueron mayores en el grupo usando lente de contacto (p=0.048). Al cuarto día postquirúrgico se encontró un mayor porcentaje de cicatrización en el grupo usando lente de contacto. (p=0.075). CONCLUSIONES: El cierre por afrontamiento con uso de lente de contacto mostró dolor y picadas mayores al primer y cuarto día postoperatorio. Pero la epitelización y cicatrización fueron tempranas con un retorno corto a actividades cotidianas.

Conocimientos, actitudes y prácticas sobre tuberculosis en indígenas zenúes y habitantes de una zona rural colombiana

Los asentamientos indígenas y los habitantes de zonas rurales presentan un elevado riesgo de padecertuberculosis. Las estrategias de promoción de la salud y prevención de la enfermedad debenacompañarse de los conocimientos, actitudes y prácticas (CAP) que las comunidades tienen sobreesta temática. Objetivo: describir los CAP sobre tuberculosis y su asociación con algunos aspectossociodemográficos de habitantes de zonas rurales e indígenas de Córdoba (Colombia) en 2012 yevaluar la validez y confiabilidad de la escala CAP. Materiales y métodos: estudio descriptivo transversalen 300 individuos, 100 indígenas zenúes y 200 campesinos. Los datos se recolectaron de fuenteprimaria y los análisis se realizaron con medidas de resumen, frecuencia y estadística no paramétricaen SPSS 20. Resultados: los CAP presentaron buena fiabilidad y validez de apariencia, contenido yconstructo. En conocimientos, un 76% mostró un grado satisfactorio; en las actitudes, un 77% fueinsatisfactorio y un 48% presentó buenas prácticas. No se halló asociación estadística de los CAPcon el sexo ni con las creencias religiosas; en la etnia se encontraron diferencias estadísticamentesignificativas en los conocimientos y las prácticas; la edad demostró asociación estadística con losconocimientos y la escolaridad evidenció asociación con las prácticas. Conclusión: se observó unadecuado conocimiento sobre tuberculosis, en tanto que las actitudes y las prácticas fueron insatisfactorias;los principales factores asociados con los CAP fueron etnia, edad y escolaridad.

Explorando modelos in vivo para caracterizar a microcirculação periférica : um estudo piloto

Nos últimos anos, a circulação cutânea surgiu como uma janela interessante para analisar a função microcirculatória e os mecanismos de disfunção. Tecnologias não-invasivas, incluindo a Fluxometria por Laser Doppler (FLD), gasimetria transcutânea e a Perda Transepidérmica de Água (PTEA), ajudaram a considerar a circulação cutânea como um modelo de translação útil na doença vascular. Neste estudo procurou-se avaliar o perfil de resposta de um grupo de indivíduos jovens saudáveis ​​(n = 8), de ambos os sexos (24,5 ± 0,8 anos de idade) a três manobras de condicionamento da perfusão no membro inferior - A: elevação da perna enquanto sentado, B: elevação da perna enquanto em decúbito dorsal; C: oclusão supra-sistólica com um torniquete. As técnicas de medição incluiram FLD, pressões parciais transcutâneas (tc) pO2 e pCO2 por gasimetria e PTEA por evaporimetria. Foram aplicados testes de estatística descritiva e não paramétrica, sendo adotado um nível de confiança de 95%. As tcpO2 e tcpCO2 alteraram-se significativamente durante as manobras. Foi registado um perfil de evolução recíproca para FLD e PTEA em A e C, o que pode sugerir que, sob as condições experimentais as condições de perfusão local podem influenciar a função epidérmica "barreira". Os modelos propostos parecem ser adequados para caracterizar a microcirculação periférica in vivo, o que justifica estudos de desenvolvimento posteriores.

Sample size determination for kernel regression estimation using sequential fixed-width confidence bands

We consider a random design model based on independent and identically distributed pairs of observations (Xi, Yi), where the regression function m(x) is given by m(x) = E(Yi|Xi = x) with one independent variable. In a nonparametric setting the aim is to produce a reasonable approximation to the unknown function m(x) when we have no precise information about the form of the true density, f(x) of X. We describe an estimation procedure of non-parametric regression model at a given point by some appropriately constructed fixed-width (2d) confidence interval with the confidence coefficient of at least 1−. Here, d(> 0) and 2 (0, 1) are two preassigned values. Fixed-width confidence intervals are developed using both Nadaraya-Watson and local linear kernel estimators of nonparametric regression with data-driven bandwidths. The sample size was optimized using the purely and two-stage sequential procedures together with asymptotic properties of the Nadaraya-Watson and local linear estimators. A large scale simulation study was performed to compare their coverage accuracy. The numerical results indicate that the confi dence bands based on the local linear estimator have the better performance than those constructed by using Nadaraya-Watson estimator. However both estimators are shown to have asymptotically correct coverage properties.