1,720,955 research outputs found
Robust estimators for functional quadratic regression models
No full textLa mayoría de los procedimientos estadísticos clásicos están basados en modelos con hipótesis rígidas, tales como errores normales u observaciones equidistribuídas, entre otros. Bajo estas hipótesis, se deducen procedimientos óptimos. Sin embargo, estos métodos son muy sensibles al incumplimiento de las hipótesis que los generaron. Los métodos estadísticos robustos tienen como objetivo permitir inferencias válidas cuando el modelo no se cumple exactamente y, al mismo tiempo, ser altamente eficientes bajo el modelo central. Por otra parte y en muchas aplicaciones, los datos observados provienen de fenómenos que son continuos en el tiempo o en el espacio y que pueden ser supuestos como curvas o funciones suaves más que como vectores de dimensión finita. El análisis de datos funcionales ha recibido considerable atención por su versatilidad en estos contextos. Cabe mencionar que el análisis de este tipo de datos requiere herramientas propias ya que, en muchas ocasiones, las extensiones naturales de las técnicas estadísticas multivariadas usuales no son adecuadas. El objetivo de esta tesis de maestría es hacer una revisión bibliográfica del tema, en particular, de los procedimientos existentes para estimar los parámetros en un modelo regresión funcional cuando las covariables son funcionales y cumplen un modelo lineal o cuadrático, a la vez que proponer estimadores robustos de los parámetros involucrados. En particular, se considera el modelo cuadrático dado en Yao y Müller (2010) y en Horváth y Reeder (2013), así como sus propuestas de estimación. Como la presencia de valores atípicos en las covariables funcionales puede afectar el procedimiento de estimación cuando se utilizan las componentes principales muestrales para reducir la dimensión y estimar los parámetros de la regresión, se definen estimadores robustos para el modelo cuadrático utilizando estimadores de las direcciones principales esféricas (Locantore et al., 1999; Gervini, 2008). Más específicamente, proponemos usar estimadores robustos de las direcciones principales para generar los espacios de dimensión finita que constituyen los posibles candidatos tanto para el parámetro de regresión funcional como el operador cuadrático, para luego usar MM−estimadores de regresión (Yohai, 1987). Se analiza la sensibilidad de estos estimadores ante la presencia de distintos porcentajes de datos atípicos, tanto en los residuos como en las covariables emulando las propuestas de simulación de Yao y Müller (2010) y Boente et al. (2020). Por último, se aplican estas técnicas a dos conjuntos de datos espectrales diferentes, ambos conocidos por presentar observaciones atípicas.Most classical statistical procedures rely on models with rigid assumptions, such as normal distributed errors or equidistributed observations, among others. Under these hypotheses, optimal procedures are obtained. However, these methods are very sensitive to non–compliance with the hypotheses that generated them. Robust statistical methods aim to allow benchmarks when the model does not hold exactly being, at the same time, highly efficient under the central model. On the other hand, in many applications the observed data come from phenomena that are continuous in time or space and can be assumed to be curves or smooth functions rather than fine–dimensional vectors. Functional data analysis has received considerable attention for its versatility in these contexts. In most situations, the analysis of these type of data requires proper tools since the natural extension of the usual multivariate statistical procedures fail. The purpose of this master’s thesis is to review the existing procedures to estimate the parameters under a functional regression model, that is, when the covariates are functional. We focus our attention on the linear and quadratic models and we propose robust estimators for the parameters involved. In particular, we consider the extension of the quadratic case as in Yao y Müller (2010) and in Horváth y Reeder (2013), as well as their estimation proposals. Since the presence of outliers in the functional covariates may affect the estimation procedure when the sample principal components are used to reduce dimensionality when estimating the regression parameters, we define robust estimators for the quadratic model using the spherical principal component basis (Locantore et al., 1999; Gervini, 2008). More specifically, we consider robust estimators for the principal directions to define a basis of possible candidates for the estimators of both the functional regression parameter and the quadratic operator, and then we use MM−regression estimators (Yohai, 1987). We analyze the sensitivity and performance of these estimators in the presence of atypical data, both in the residuals and in the covariates, emulating the simulation proposals of Yao y Müller (2010) and Boente et al. (2020). Finally, we apply these procedures on two datasets of different spectral data, both known to have outliers.Fil: Parada, Daniela Laura. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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