Results 1  10
of
205
Cluster Ensembles  A Knowledge Reuse Framework for Combining Multiple Partitions
 Journal of Machine Learning Research
, 2002
"... This paper introduces the problem of combining multiple partitionings of a set of objects into a single consolidated clustering without accessing the features or algorithms that determined these partitionings. We first identify several application scenarios for the resultant 'knowledge reuse&ap ..."
Abstract

Cited by 603 (20 self)
 Add to MetaCart
This paper introduces the problem of combining multiple partitionings of a set of objects into a single consolidated clustering without accessing the features or algorithms that determined these partitionings. We first identify several application scenarios for the resultant 'knowledge reuse' framework that we call cluster ensembles. The cluster ensemble problem is then formalized as a combinatorial optimization problem in terms of shared mutual information. In addition to a direct maximization approach, we propose three effective and efficient techniques for obtaining highquality combiners (consensus functions). The first combiner induces a similarity measure from the partitionings and then reclusters the objects. The second combiner is based on hypergraph partitioning. The third one collapses groups of clusters into metaclusters which then compete for each object to determine the combined clustering. Due to the low computational costs of our techniques, it is quite feasible to use a supraconsensus function that evaluates all three approaches against the objective function and picks the best solution for a given situation. We evaluate the effectiveness of cluster ensembles in three qualitatively different application scenarios: (i) where the original clusters were formed based on nonidentical sets of features, (ii) where the original clustering algorithms worked on nonidentical sets of objects, and (iii) where a common dataset is used and the main purpose of combining multiple clusterings is to improve the quality and robustness of the solution. Promising results are obtained in all three situations for synthetic as well as real datasets.
Coclustering documents and words using Bipartite Spectral Graph Partitioning
, 2001
"... ..."
(Show Context)
Clustering with Bregman Divergences
 JOURNAL OF MACHINE LEARNING RESEARCH
, 2005
"... A wide variety of distortion functions are used for clustering, e.g., squared Euclidean distance, Mahalanobis distance and relative entropy. In this paper, we propose and analyze parametric hard and soft clustering algorithms based on a large class of distortion functions known as Bregman divergence ..."
Abstract

Cited by 443 (57 self)
 Add to MetaCart
(Show Context)
A wide variety of distortion functions are used for clustering, e.g., squared Euclidean distance, Mahalanobis distance and relative entropy. In this paper, we propose and analyze parametric hard and soft clustering algorithms based on a large class of distortion functions known as Bregman divergences. The proposed algorithms unify centroidbased parametric clustering approaches, such as classical kmeans and informationtheoretic clustering, which arise by special choices of the Bregman divergence. The algorithms maintain the simplicity and scalability of the classical kmeans algorithm, while generalizing the basic idea to a very large class of clustering loss functions. There are two main contributions in this paper. First, we pose the hard clustering problem in terms of minimizing the loss in Bregman information, a quantity motivated by ratedistortion theory, and present an algorithm to minimize this loss. Secondly, we show an explicit bijection between Bregman divergences and exponential families. The bijection enables the development of an alternative interpretation of an ecient EM scheme for learning models involving mixtures of exponential distributions. This leads to a simple soft clustering algorithm for all Bregman divergences.
A Probabilistic Framework for SemiSupervised Clustering
, 2004
"... Unsupervised clustering can be significantly improved using supervision in the form of pairwise constraints, i.e., pairs of instances labeled as belonging to same or different clusters. In recent years, a number of algorithms have been proposed for enhancing clustering quality by employing such supe ..."
Abstract

Cited by 275 (14 self)
 Add to MetaCart
(Show Context)
Unsupervised clustering can be significantly improved using supervision in the form of pairwise constraints, i.e., pairs of instances labeled as belonging to same or different clusters. In recent years, a number of algorithms have been proposed for enhancing clustering quality by employing such supervision. Such methods use the constraints to either modify the objective function, or to learn the distance measure. We propose a probabilistic model for semisupervised clustering based on Hidden Markov Random Fields (HMRFs) that provides a principled framework for incorporating supervision into prototypebased clustering. The model generalizes a previous approach that combines constraints and Euclidean distance learning, and allows the use of a broad range of clustering distortion measures, including Bregman divergences (e.g., Euclidean distance and Idivergence) and directional similarity measures (e.g., cosine similarity). We present an algorithm that performs partitional semisupervised clustering of data by minimizing an objective function derived from the posterior energy of the HMRF model. Experimental results on several text data sets demonstrate the advantages of the proposed framework. 1.
Semisupervised Clustering by Seeding
 In Proceedings of 19th International Conference on Machine Learning (ICML2002
, 2002
"... Semisupervised clustering uses a small amount of labeled data to aid and bias the clustering of unlabeled data. This paper explores the use of labeled data to generate initial seed clusters, as well as the use of constraints generated from labeled data to guide the clustering process. It intr ..."
Abstract

Cited by 209 (17 self)
 Add to MetaCart
Semisupervised clustering uses a small amount of labeled data to aid and bias the clustering of unlabeled data. This paper explores the use of labeled data to generate initial seed clusters, as well as the use of constraints generated from labeled data to guide the clustering process. It introduces two semisupervised variants of KMeans clustering that can be viewed as instances of the EM algorithm, where labeled data provides prior information about the conditional distributions of hidden category labels. Experimental results demonstrate the advantages of these methods over standard random seeding and COPKMeans, a previously developed semisupervised clustering algorithm.
Active SemiSupervision for Pairwise Constrained Clustering
 Proc. 4th SIAM Intl. Conf. on Data Mining (SDM2004
"... Semisupervised clustering uses a small amount of supervised data to aid unsupervised learning. One typical approach specifies a limited number of mustlink and cannotlink constraints between pairs of examples. This paper presents a pairwise constrained clustering framework and a new method for acti ..."
Abstract

Cited by 136 (9 self)
 Add to MetaCart
(Show Context)
Semisupervised clustering uses a small amount of supervised data to aid unsupervised learning. One typical approach specifies a limited number of mustlink and cannotlink constraints between pairs of examples. This paper presents a pairwise constrained clustering framework and a new method for actively selecting informative pairwise constraints to get improved clustering performance. The clustering and active learning methods are both easily scalable to large datasets, and can handle very high dimensional data. Experimental and theoretical results confirm that this active querying of pairwise constraints significantly improves the accuracy of clustering when given a relatively small amount of supervision. 1
Efficient Clustering Of Very Large Document Collections
, 2001
"... An invaluable portion of scientific data occurs naturally in text form. Given a large unlabeled document collection, it is often helpful to organize this collection into clusters of related documents. By using a vector space model, text data can be treated as highdimensional but sparse numerical da ..."
Abstract

Cited by 115 (10 self)
 Add to MetaCart
An invaluable portion of scientific data occurs naturally in text form. Given a large unlabeled document collection, it is often helpful to organize this collection into clusters of related documents. By using a vector space model, text data can be treated as highdimensional but sparse numerical data vectors. It is a contemporary challenge to efficiently preprocess and cluster very large document collections. In this paper we present a time and memory ecient technique for the entire clustering process, including the creation of the vector space model. This efficiency is obtained by (i) a memoryecient multithreaded preprocessing scheme, and (ii) a fast clustering algorithm that fully exploits the sparsity of the data set. We show that this entire process takes time that is linear in the size of the document collection. Detailed experimental results are presented  a highlight of our results is that we are able to effectively cluster a collection of 113,716 NSF award abstracts in 23 minutes (including disk I/O costs) on a single workstation with modest memory consumption.
Semisupervised graph clustering: a kernel approach
, 2008
"... Semisupervised clustering algorithms aim to improve clustering results using limited supervision. The supervision is generally given as pairwise constraints; such constraints are natural for graphs, yet most semisupervised clustering algorithms are designed for data represented as vectors. In this ..."
Abstract

Cited by 94 (3 self)
 Add to MetaCart
(Show Context)
Semisupervised clustering algorithms aim to improve clustering results using limited supervision. The supervision is generally given as pairwise constraints; such constraints are natural for graphs, yet most semisupervised clustering algorithms are designed for data represented as vectors. In this paper, we unify vectorbased and graphbased approaches. We first show that a recentlyproposed objective function for semisupervised clustering based on Hidden Markov Random Fields, with squared Euclidean distance and a certain class of constraint penalty functions, can be expressed as a special case of the weighted kernel kmeans objective (Dhillon et al., in Proceedings of the 10th International Conference on Knowledge Discovery and Data Mining, 2004a). A recent theoretical connection between weighted kernel kmeans and several graph clustering objectives enables us to perform semisupervised clustering of data given either as vectors or as a graph. For graph data, this result leads to algorithms for optimizing several new semisupervised graph clustering objectives. For vector data, the kernel approach also enables us to find clusters with nonlinear boundaries in the input data space. Furthermore, we show that recent work on spectral learning (Kamvar et al., in Proceedings of the 17th International Joint Conference on Artificial Intelligence, 2003) may be viewed as a special case of our formulation. We empirically show that our algorithm is able to outperform current stateoftheart semisupervised algorithms on both vectorbased and graphbased data sets.
Exploiting hierarchical domain structure to compute similarity
 ACM Trans. Inf. Syst
"... The notion of similarity between objects nds use in many contexts, e.g., in search engines, collaborative ltering, and clustering. Objects being compared often are modeled as sets, with their similarity traditionally determined based on set intersection. Intersectionbased measures do not accurately ..."
Abstract

Cited by 84 (0 self)
 Add to MetaCart
The notion of similarity between objects nds use in many contexts, e.g., in search engines, collaborative ltering, and clustering. Objects being compared often are modeled as sets, with their similarity traditionally determined based on set intersection. Intersectionbased measures do not accurately capture similarity in certain domains, such as when the data is sparse or when there are known relationships between items within sets. We propose new measures that exploit a hierarchical domain structure in order to produce more intuitive similarity scores. We also extend our similarity measures to provide appropriate results in the presence of multisets (also handled unsatisfactorily by traditional measures), e.g., to correctly compute the similarity between customers who buy several instances of the same product (say milk), or who buy several products in the same category (say dairy products). We also provide an experimental comparison of our measures against traditional similarity measures, and describe an informal user study that evaluated how well our measures match human intuition. 1
Clickstream Clustering Using Weighted Longest Common Subsequences
 In Proceedings of the Web Mining Workshop at the 1st SIAM Conference on Data Mining
, 2001
"... Categorizing visitors based on their interactions with a website is a key problem in web usage mining. The clickstreams generated by various users often follow distinct patterns, the knowledge of which may help in providing customized content. In this paper, we propose a novel and effective algorith ..."
Abstract

Cited by 78 (4 self)
 Add to MetaCart
(Show Context)
Categorizing visitors based on their interactions with a website is a key problem in web usage mining. The clickstreams generated by various users often follow distinct patterns, the knowledge of which may help in providing customized content. In this paper, we propose a novel and effective algorithm for clustering webusers based on a function of the longest common subsequence of their clickstreams that takes into account both the trajectory taken through a website and the time spent at each page. Results are presented on weblogs of www.sulekha.com to illustrate the techniques.