Robust sparse principal component analysis.

A method for principal component analysis is proposed that is sparse and robust at the same time. The sparsity delivers principal components that have loadings on a small number of variables, making them easier to interpret. The robustness makes the analysis resistant to outlying observations. The principal components correspond to directions that maximize a robust measure of the variance, with an additional penalty term to take sparseness into account. We propose an algorithm to compute the sparse and robust principal components. The method is applied on several real data examples, and diagnostic plots for detecting outliers and for selecting the degree of sparsity are provided. A simulation experiment studies the loss in statistical efficiency by requiring both robustness and sparsity.Dispersion measure; Projection-pursuit; Outliers; Variable selection;

Considerações sobre o texto de Christophe Pons: “Ocultismo e Protestantismo na Islândia: Tendências iconófilas de contextos não-icônicos”

Reação ao texto principal de Christophe Pons. [Tradução: Felipe Gustavo Koch Buttelli

Erwägungen zu Christophe Pons “Ocultismo e Protestantismo na Islândia: Tendências iconófilas de contextos não-icônicos”

Reação ao texto principal de Christophe Pon

Dialogues and Dynamics – Interculturality in Theology and Religious Studies

This volume contains the texts from the symposium on the occasion of the 10th Anniversary of the M.A. Programme Intercultural Theology. The contributions address the challenges and consequences of an intercultural approach in academics as well as in the churches and in society. Since globalisation has significantly changed the face of contemporary Christianity in the 21st century, the task of doing theology has become more complex. The cultural, geographic and denominational varieties of Christianity worldwide challenge the traditional Western face of academic Christian theology and demand new and global forms of theological thinking across lines. Intercultural Theology seeks to embrace these dynamics with a constructive dialogue, opening up new spaces of collaborative thinking and academic reflection

tclust: An R Package for a Trimming Approach to Cluster Analysis

Outlying data can heavily influence standard clustering methods. At the same time, clustering principles can be useful when robustifying statistical procedures. These two reasons motivate the development of feasible robust model-based clustering approaches. With this in mind, an R package for performing non-hierarchical robust clustering, called tclust, is presented here. Instead of trying to “fit” noisy data, a proportion α of the most outlying observations is trimmed. The tclust package efficiently handles different cluster scatter constraints. Graphical exploratory tools are also provided to help the user make sensible choices for the trimming proportion as well as the number of clusters to search for

Robust constrained fuzzy clustering

It is well-known that outliers and noisy data can be very harmful when applying clustering methods. Several fuzzy clustering methods which are able to handle the presence of noise have been proposed. In this work, we propose a robust clustering approach called F-TCLUST based on an “impartial” (i.e., self-determined by data) trimming. The proposed approach considers an eigenvalue ratio constraint that makes it a mathematically well-defined problem and serves to control the allowed differences among cluster scatters. A computationally feasible algorithm is proposed for its practical implementation. Some guidelines about how to choose the parameters controlling the performance of the fuzzy clustering procedure are also given.Estadística e I

A fast algorithm for robust constrained clustering

The application of “concentration” steps is the main principle behind Forgy’s k-means algorithm and Rousseeuw and van Driessen’s fast-MCD algorithm. Despite this coincidence, it is not completely straightforward to combine both algorithms for developing a clustering method which is not severely affected by few outlying observations and being able to cope with non spherical clusters. A sensible way of combining them relies on controlling the relative cluster scatters through constrained concentration steps. With this idea in mind, a new algorithm for the TCLUST robust clustering procedure is proposed which implements such constrained concentration steps in a computationally efficient fashion.Estadística e I

Ecumenism as a global player - what moves the world and what moves ecumenic

Schäfer H. Ökumene als global player - Was bewegt die Welt und was die Ökumene? In: Erich F, ed. Rekonfiguration. Oder: Die ökumenische Bewegung in Zeiten der Globalisierung. Loccumer Protokoll. Vol 58/04. Rehburg-Loccum.; 2005

Technikfolgen-Abschätzung zum Raumtransportsystem "SÄNGER"

Kapitel I der Studie enthält eine Übersicht über die heute verfügbaren Raumtransportsysteme und eine Analyse ihrer Hauptdefizite. Aus dieser Defizitanalyse werden Anforderungen an zukünftige Raumtransportsysteme abgeleitet. Abschließend werden die wichtigsten derzeit diskutierten Konzepte für Raumtransportsysteme der nächsten Generation" - darunter das Konzept SÄNGER - dargestellt. In Kapitel II werden Konzeption, Ablauf und Organisation des deutschen Hyperschalltechnologie-Programms und die mit diesem Programm bzw. einem zukünftigen Raumtransportsystem vom Typ SÄNGER verfolgten Ziele beschrieben. Bei diesen Zielen handelt es sich fast überwiegend um "Optimierungsziele" - Raumtransporte sollen in Zukunft z.B. wirtschaftlicher, sicherer, umweltfreundlicher werden -, die den Bedarf nach Raumtransporten und Raumtransportsystemen· voraussetzen. Der Frage des Bedarfs wird in Kapitel III nachgegangen. Nach einer Darstellung der kontroversen Diskussion um den gesellschaftlichen Nutzen der Raumfahrt und der in dieser Diskussion vertretenen Positionen werden zwei von der DLR in ihrem Gutachten entwickelte raumfahrtpolitische Nutzungsszenarien, beschrieben und diskutiert, insbesondere auch im Hinblick auf darin enthaltene mögliche zukünftige "Marktsegmente" für ein Raumtransportsystem vom Typ SÄNGER. In Kapitel IV werden die mit dem Hyperschalltechnologie-Programm bzw. einem zukünftigen System SÄNGER verfolgten Zielsetzungen eingehend analysiert: Reduzierung der Kosten des Raumtransports; Erhöhung der Sicherheit und Zuverlässigkeit des Raumtransports; Verbesserung der Umweltverträglichkeit des Raumtransports; Durchführung des Raumtransports von europäischen Flugplätzen; Verbesserung der technologischen Basis für zukünftige Projekte der Luft- und Raumfahrt sowie für andere Gebiete der Hochtechnologie ("Spin-off“); technologische Vorbereitung der "nächsten Generation" von Raumtransportsystemen. In Kapitel V wird - ausgehend von den Ergebnissen der vorangehenden Kapitel - der politische Entscheidungsbedarf bezüglich des Hyperschalltechnologie-Programms und des Leitkonzepts SÄNGER zusammenfassend dargestellt. Abschließend werden politische Handlungsoptionen diskutiert