Streaming data is one of the attention receiving sources for concept-evolution studies. When a new class occurs in the data stream it can be considered as a new concept and so the concept-evolution. One attractive problem occurring in the concept-evolution studies is the recurring classes from our previous study. In data streams, a class can disappear and reappear after a while. Existing studies on data stream classification techniques either misclassify the recurring class or falsely identify the recurring classes as novel classes. Because of the misclassification or false novel classification, the error rates increases on those studies. In this paper we address the problem by defining a novel ensemble technique “class-based” ensemble which replaces the traditional “chunk-based” approach in order to detect the recurring classes. We discuss the details of two different approaches in class-based ensemble and explain and compare them in detail. Different than the previous studies in the field, we also prove the superiority of both “class-based” ensemble method over state-of-art techniques via empirical approach on a number of benchmark data sets including web comments as text mining challenge.

Recurring and Novel Class Detection Using Class-Based Ensemble for Evolving Data Stream

In cluster-based wireless sensor networks, cluster heads (CHs) gather and fuse data packets from sensor nodes; then, they forward fused packets to the sink node (SN). This helps wireless sensor networks balance energy effectively and efficiently to prolong their lifetime. However, cluster-based WSNs are vulnerable to selective forwarding attacks. Compromised CHs would become malicious and launch selective forwarding attacks in which they drop part of or all the packets from other nodes. In this paper, a data clustering algorithm (DCA) for detecting a selective forwarding attack (DCA-SF) is proposed. It can capture and isolate malicious CHs that have launched selective forwarding attacks by clustering their cumulative forwarding rates (CFRs). The DCA-SF algorithm has been strengthened by changing the DCA parameters (Eps, Minpts) adaptively. The simulation results show that the DCA-SF has a low missed detection rate of 1.04% and a false detection rate of 0.42% respectively with low energy consumption.

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A Data Clustering Algorithm for Detecting Selective Forwarding Attack in Cluster-Based Wireless Sensor Networks

Density Peaks Clustering (DPC) is a density-based clustering algorithm that has the advantage of not requiring clustering parameters and detecting non-spherical clusters. The density peaks algorithm obtains the actual cluster center by inputting the cutoff distance and manually selecting the cluster center. Thus, the clustering center point is not selected on the basis of considering the whole data set. This paper proposes a method called G-KNN-DPC to calculate the cutoff distance based on the Gini coefficient and K-nearest neighbor. G-KNN-DPC first finds the optimal cutoff distance with Gini coefficient, and then the center point with the K-nearest neighbor. The automatic clustering center method can not only avoid the error that a cluster detects two center points but also effectively solve the traditional DPC algorithm defect that cannot handle complex data sets. Compared with DPC, Fuzzy C-Means, K-means, KDPC and DBSCAN, the proposed algorithm creates better clusters on different data sets.

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Adaptive Density Peaks Clustering Based on K-Nearest Neighbor and Gini Coefficient

Density Peak Clustering (DPC), a popular density-based clustering approach, has received considerable attention from the research community primarily due to its simplicity and fewer-parameter requirement. However, the resultant clusters obtained using DPC are influenced by the sensitive parameter $d_c$, which depends on data distribution and requirements of different users. Besides, the original DPC algorithm requires visiting a large number of objects, making it slow. To this end, this paper investigates index-based solutions for DPC. Specifically, we propose two list-based index methods viz. (i) a simple List Index, and (ii) an advanced Cumulative Histogram Index. Efficient query algorithms are proposed for these indices which significantly avoids irrelevant comparisons at the cost of space. For memory-constrained systems, we further introduce an approximate solution to the above indices which allows substantial reduction in the space cost, provided that slight inaccuracies are admissible. Furthermore, owing to considerably lower memory requirements of existing tree-based index structures, we also present effective pruning techniques and efficient query algorithms to support DPC using the popular Quadtree Index and R-tree Index. Finally, we practically evaluate all the above indices and present the findings and results, obtained from a set of extensive experiments on six synthetic and real datasets. The experimental insights obtained can help to guide in selecting a befitting index.

Index-based Solutions for Efficient Density Peak Clustering

Density-based clustering algorithms have the distinctive advantage of discovering arbitrarily shaped clusters, but they usually require a procedure to compute the distance between every pair of data points, and this procedure is prohibitive for large datasets since it has quadratic computation complexity. In this paper, we propose a new distributed clustering algorithm, named REstore MOdel with Local Density estimation (REMOLD). Firstly, REMODL applies a balanced partitioning method to evenly divide an large dataset based on Local Sensitive Hashing (LSH). Then, it locally clusters each partition of the dataset, and uses a Gaussian model to represent each local cluster based on the observation that the density distribution of each local cluster shares similar shape with Gaussian distribution. Finally, these models are aggregated on a server where REMOLD restores global clusters based on these local Gaussian models. More specifically, model connection, which measures the density connectivity between two models, are defined to merge local models with an optimized procedure. In this aggregation, REMOLD requires low cost of network transmission for local Gaussian models, since the number of Gaussian models is often less than that of core objects for each partition. We evaluate REMOLD on three synthetic datasets and three real-world datasets on Spark, and the experiment results demonstrate that REMOLD is efficient and effective to find out clusters with complex shapes and it outperforms the established methods.

REMOLD: An Efficient Model-Based Clustering Algorithm for Large Datasets with Spark

-Density Peaks (DP) is a recently proposed clustering algorithm that has distinctive advantages over existing clustering algorithms It has already been used in a wide range of applications However, DP requires computing the distance between every pair of input points, therefore incurring quadratic computation overhead, which is prohibitive for large data sets In this paper, we propose an efficient distributed algorithm LSHDDP, which is an approximate algorithm that exploits Locality Sensitive Hashing We present formal analysis of LSH-DDP, and show that the approximation quality and the runtime can be controlled by tuning the parameters of LSH-DDP Experimental results on both a local cluster and EC2 show that LSH-DDP achieves a factor of 17-70x speedup over the na¨ive distributed DP implementation and 2x speedup over the state-of-the-art EDDPC approach, while returning comparable cluster results

Shimin Cheny

Papers

Efficient Distributed Density Peaks for Clustering Large Data Sets in MapReduce