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The Global ETD Search service is a free service for researchers
to find electronic theses and dissertations. This service is
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Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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Showing 1 to 3 of 3 (0.041 seconds)Spelling suggestions: "subject:"R < dendrogramm> "" "subject:"R < bildprogramm> ""
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FlexMix: A general framework for finite mixture models and latent class regression in RLeisch, Friedrich January 2003 (has links) (PDF)
Flexmix implements a general framework for fitting discrete mixtures of regression models in the R statistical computing environment: three variants of the EM algorithm can be used for parameter estimation, regressors and responses may be multivariate with arbitrary dimension, data may be grouped, e.g., to account for multiple observations per individual, the usual formula interface of the S language is used for convenient model specification, and a modular concept of driver functions allows to interface many di_erent types of regression models. Existing drivers implement mixtures of standard linear models, generalized linear models and model-based clustering. Flexmix provides the E-step and all data handling, while the M-step can be supplied by the user to easily define new models. (author's abstract) / Series: Report Series SFB "Adaptive Information Systems and Modelling in Economics and Management Science"
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DirichletReg: Dirichlet Regression for Compositional Data in RMaier, Marco J. 18 January 2014 (has links) (PDF)
Dirichlet regression models can be used to analyze a set of variables lying
in a bounded interval that sum up to a constant (e.g., proportions, rates,
compositions, etc.) exhibiting skewness and heteroscedasticity, without
having to transform the data.
There are two parametrization for the presented model, one using the common
Dirichlet distribution's alpha parameters, and a reparametrization of the
alpha's to set up a mean-and-dispersion-like model.
By applying appropriate link-functions, a GLM-like framework is set up that
allows for the analysis of such data in a straightforward and familiar way,
because interpretation is similar to multinomial logistic regression.
This paper gives a brief theoretical foundation and describes the
implementation as well as application (including worked examples) of
Dirichlet regression methods implemented in the package DirichletReg (Maier,
2013) in the R language (R Core Team, 2013). (author's abstract) / Series: Research Report Series / Department of Statistics and Mathematics
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Improving the predictive capability of the soil erosion modeling tool EROSION-3D: From observation data to validationLenz, Jonas 16 May 2023 (has links)
Ziel dieser Arbeit ist die Verbesserung der Vorhersagekraft des Bodenerosionsmodelierungs-werkzeugs EROSION-3D, welche oftmals durch die Identifizierung der werkzeugspezifischen Parameter Skinfaktor und Erosionswiderstand limitiert ist.
Als drei Betrachtungsebenen der Arbeit werden 1. Beobachtungsdaten, 2. die Fähigkeit von EROSION-3D zur Beschreibung der Beobachtungsdaten und 3. die Vorhersagekraft des Werkzeugs untersucht. Aufzeichnungen verschiedener Beregnungsversuche wurden maschinenlesbar zusammengefasst. Daran wurde EROSION-3D mit den bisher üblichen sowie Monte-Carlo Methoden kalibriert. Anhand beschreibender Daten der Beregnungsversuche wurden Vorhersagemethoden zur Schätzung der modellspezifischen Parameter entwickelt und hinsichtlich der Parameterwerte und damit modellierter Abfluss-/Abtragswerte validiert.
Die Ergebnisse zeigen, dass verbesserte Vorhersagen mit den neuen Schätzmethoden möglich sind, aber auch Möglichkeiten zur Verbesserung der Modellstruktur bestehen.
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