PhD ceremony: Ms. P. Schneider, 14.45 uur, Academiegebouw, Broerstraat 5, Groningen
Thesis: Advanced methods for prototype-based classification
Promotor(s): prof. M. Biehl, prof. N. Petkov
Faculty: Mathematics and Natural Sciences
The thesis presents research on Learning Vector Quantization (LVQ). LVQ is a simple and intuitive classification technique: LVQ algorithms learn prototypical vectors for the classes of the considered data set. The prototypes are used for a distance-based classification, i.e. a patter is assigned to the class represented by the closest prototype with respect to a certain distance measure.
The thesis deals with two issues: a new approach for metric adaptation in LVQ is presented and modifications of one specific learning algorithm, namely Robust Soft LVQ, are introduced.
Metric adaptation techniques allow to learn problem specific distance measures from the training data. Since the classifier's decision depends on distances between prototypes and feature vectors, the selected metric is a key issue for the performance of LVQ. We extend the Euclidean distance by a matrix of adaptive weight values. The diagonal entries of the matrix quantify the importance of single features for classification while off-diagonal elements correspond to the relevance of pairs in the classification scheme. Practical applications show that the advanced metric allows to improve the classification of the employed algorithms significantly. Furthermore, the metric parameters provide insight into the nature of the data. The convergence behaviour of the training algorithms is also analysed theoretically.
The proposed modifications of Robust Soft LVQ concern the treatment of the algorithm's hyperparameter, the decision rule for classification, and we present a generalization of the algorithm with respect to vectorial class labels of the input data. The methods are illustrated by means of practical experiments.
Three researchers of the Faculty of Science and Engineering have been awarded an ENW-XS grant by the Dutch Research Council (Nederlandse Organisatie voor Wetenschappelijke Onderzoek, NWO): Prof. A.I. Guskov the Groningen Biomolecular Sciences and...
Bayu Jayawardhana has been appointed scientific director of DISC, the interuniversity research institute and graduate school that unites all university groups in the Netherlands that are active in systems and control theory and engineering. The...
Researchers Clemens Mayer and Danny Incarnato of the University of Groningen have been awarded an ERC Consolidator Grant.
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