Partitional Clustering

People are living in a world full of data. Humans are collecting data from many measurements and observations in their daily works. The sorting of these numerous data is important and necessary in terms of analyzing, reasoning, and decision-making processes. For this reason, clustering has been used in many areas and has become very important in recent years. Feature selection and classifying the data in subsets can be changed data to data. As a result of these feature selection methods, some clustering methods have been revealed. Hierarchical clustering, partitional clustering, artificial system clustering, kernel-based clustering, and sequential data clustering are determined for different clustering strategies. This chapter examines some popular partitional clustering techniques and algorithms. Partitional clustering assigns a set of data points into k-clusters by using iterative processes. The predefined criterion function (J) assigns the datum into kth number set. As a result of this criterion function value in k sets (maximization and minimization calculation), clustering can be done. This chapter starts with criterion function for clustering process. In addition, some applications will be done for each algorithm in this chapter

Linear, Deterministic, and Order-Invariant Initialization Methods for the K-Means Clustering Algorithm

Over the past five decades, k-means has become the clustering algorithm of choice in many application domains primarily due to its simplicity, time/space efficiency, and invariance to the ordering of the data points. Unfortunately, the algorithm's sensitivity to the initial selection of the cluster centers remains to be its most serious drawback. Numerous initialization methods have been proposed to address this drawback. Many of these methods, however, have time complexity superlinear in the number of data points, which makes them impractical for large data sets. On the other hand, linear methods are often random and/or sensitive to the ordering of the data points. These methods are generally unreliable in that the quality of their results is unpredictable. Therefore, it is common practice to perform multiple runs of such methods and take the output of the run that produces the best results. Such a practice, however, greatly increases the computational requirements of the otherwise highly efficient k-means algorithm. In this chapter, we investigate the empirical performance of six linear, deterministic (non-random), and order-invariant k-means initialization methods on a large and diverse collection of data sets from the UCI Machine Learning Repository. The results demonstrate that two relatively unknown hierarchical initialization methods due to Su and Dy outperform the remaining four methods with respect to two objective effectiveness criteria. In addition, a recent method due to Erisoglu et al. performs surprisingly poorly.Comment: 21 pages, 2 figures, 5 tables, Partitional Clustering Algorithms (Springer, 2014). arXiv admin note: substantial text overlap with arXiv:1304.7465, arXiv:1209.196

Web User Session Characterization via Clustering Techniques

We focus on the identification and definition of "Web user-sessions", an aggregation of several TCP connections generated by the same source host on the basis of TCP connection opening time. The identification of a user session is non trivial; traditional approaches rely on threshold based mechanisms, which are very sensitive to the value assumed for the threshold and may be difficult to correctly set. By applying clustering techniques, we define a novel methodology to identify Web user-sessions without requiring an a priori definition of threshold values. We analyze the characteristics of user sessions extracted from real traces, studying the statistical properties of the identified sessions. From the study it emerges that Web user-sessions tend to be Poisson, but correlation may arise during periods of network/hosts anomalous functioning