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SemiSupervised Metric Learning Using Pairwise Constraints
"... Distance metric has an important role in many machine learning algorithms. Recently, metric learning for semisupervised algorithms has received much attention. For semisupervised clustering, usually a set of pairwise similarity and dissimilarity constraints is provided as supervisory information. ..."
Abstract

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Distance metric has an important role in many machine learning algorithms. Recently, metric learning for semisupervised algorithms has received much attention. For semisupervised clustering, usually a set of pairwise similarity and dissimilarity constraints is provided as supervisory information. Until now, various metric learning methods utilizing pairwise constraints have been proposed. The existing methods that can consider both positive (mustlink) and negative (cannotlink) constraints find linear transformations or equivalently global Mahalanobis metrics. Additionally, they find metrics only according to the data points appearing in constraints (without considering other data points). In this paper, we consider the topological structure of data along with both positive and negative constraints. We propose a kernelbased metric learning method that provides a nonlinear transformation. Experimental results on synthetic and realworld data sets show the effectiveness of our metric learning method. 1
Learning Assignment Order of Instances for Constrained Kmeans Clustering Algorithm
, 2007
"... Constrained Kmeans clustering algorithm with instancelevel background knowledge can often achieve a better clustering solution when compared with the one obtained by traditional unsupervised Kmeans clustering algorithm. However, constrained Kmeans clustering algorithm suffers from the problem of ..."
Abstract

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Constrained Kmeans clustering algorithm with instancelevel background knowledge can often achieve a better clustering solution when compared with the one obtained by traditional unsupervised Kmeans clustering algorithm. However, constrained Kmeans clustering algorithm suffers from the problem of the sensitivity to the assignment order of instances. To the best knowledge of the authorsâ€™, very few work has been done on learning a good assignment order of instances for constrained Kmeans clustering algorithm. This paper explores the above problem and proposes a novel assignment order learning algorithm for constrained Kmeans clustering algorithm, termed as Clustering Uncertainty based assignment order Learning Algorithm (UALA). UALA ranks all instances in the data set according to their clustering uncertainty that is calculated by using the ensembles of multiple clustering algorithms. We test UALA on several real data sets with artificial instancelevel constraints. Experimental results demonstrate that UALA is able to identify a good assignment order of instances for constrained Kmeans clustering algorithm, therefore can significantly improve the accuracy of constrained Kmeans clustering algorithm. Index Terms Clustering analysis, constrained Kmeans clustering algorithm, semisupervised clustering with instancelevel constraints I.