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Saturday, February 28, 2009

Paper Review: A Comparison of Document Clustering Techniques

This paper is written by Steinback, Karpis, and Kumar, University of Minnesota, published at KDD workshop on text mining, 2000.

This paper presents the results of an experimental study of two main approaches to document clustering, agglomerative hierarchical clustering and K-means (standard K-means and bisecting K-means).

Example of Hierarchical Agglomerative Clustering (HAC)

The two basic approaches to generating a hierarchical clustering are agglomerative and divisive. The paper evaluated agglomerative techniques in the comparison. It then described the agglomerative clustering algorithm, the K-means algorithm, and the bisecting K-means algorithm in details.


Visualization of the K-means algorithm

Three evaluation metrics are used in the experiments, and they include two external quality measure, entropy, F measure, and one internal quality measure, overall similarity. The paper described each measure in detail.

Eight data sets were used in the experiments: 5 from TREC, 2 from Reuters-21578, and 1 from WebACE. Performances of three agglomerative hierarchical techniques, Intra-Cluster Similarity Technique (IST), Centroid Similarity Technique (CST), and UPGMA were compared using F-measure and entropy. UPGMA is the best performing hierarchical technique overall, therefore, its performance is compared against standard K-means and bisecting K-means. The performances of bisecting K-means with refinement and hierarchical with refinement are also included in the comparison. In the experiments, the authors used many runs of the regular K-means algorithm and also used incremental updating of centroids.

Experimental results show that the bisecting K-means technique is better than the standard K-means approach and as good or better than the hierarchical approaches when using the three evaluation metrics mentioned. Also the time complexity of bisecting K-means is linear, which makes it very attractive.

The authors argued that the agglomerative hierarchical clustering didn’t do well because nearest neighbors of documents often belong to different classes. K-means and bisecting K-means algorithms do better because they rely on a more global approach. They also believe that bisecting K-means does better than standard K-means because it produces relatively uniformly sized clusters.


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