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=== STREAM ===
STREAM is an algorithm for clustering data streams described by Guha, Mishra, Motwani and O'Callaghan<ref name=cds >{{cite journal | first1 = S. | last1 = Guha | first2 = N. | last2 = Mishra | first3 = R. | last3 = Motwani | first4 = L. | last4 = O'Callaghan | citeseerx = 10.1.1.32.1927 | title = Clustering Data Streams | journal = Proceedings of the Annual Symposium on Foundations of Computer Science | pages = 359–366 | date = 2000 | doi = 10.1109/SFCS.2000.892124 | isbn = 0-7695-0850-2 | s2cid = 2767180 }}</ref> which achieves a [[approximation algorithm|constant factor approximation]] for the k-Median problem in a single pass and using small space.
{{math theorem | STREAM can solve the ''k''-Median problem on a data stream in a single pass, with time ''O''(''n''<sup>1+''e''</sup>) and space ''θ''(''n''<sup>''ε''</sup>) up to a factor 2<sup>O(1/''e'')</sup>, where ''n'' the number of points and {{tmath|e<1/2}}.}}
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Other well-known algorithms used for data stream clustering are:
* [[BIRCH (data clustering)|BIRCH]]:<ref name="birch">{{cite journal | first1 = T. | last1 = Zhang | first2 = R. | last2 = Ramakrishnan | first3 = M. | last3 = Linvy |doi=10.1145/235968.233324 | title = BIRCH: An Efficient Data Clustering Method for Very Large Databases | journal = Proceedings of the ACM SIGMOD Conference on Management of Data | date = 1996 | volume=25 | issue = 2 | pages=103–114}}</ref> builds a hierarchical data structure to incrementally cluster the incoming points using the available memory and minimizing the amount of I/O required. The complexity of the algorithm is {{tmath|O(N)}} since one pass suffices to get a good clustering (though, results can be improved by allowing several passes).
* [[Cobweb (clustering)|COBWEB]]:<ref>{{cite journal | first = D. H. | last = Fisher | title = Knowledge Acquisition Via Incremental Conceptual Clustering | journal = Machine Learning | date = 1987 | doi=10.1023/A:1022852608280 | volume=2 | issue = 2 | pages=139–172| doi-access = free }}</ref><ref>{{cite journal | first = D. H. | last = Fisher | citeseerx = 10.1.1.6.9914 | title = Iterative Optimization and Simplification of Hierarchical Clusterings | journal = Journal of AI Research | volume = 4 | date = 1996 | doi = 10.48550/arXiv.cs/9604103 | bibcode = 1996cs........4103F | arxiv = cs/9604103 }}</ref> is an incremental clustering technique that keeps a [[hierarchical clustering]] model in the form of a [[Decision tree learning|classification tree]]. For each new point COBWEB descends the tree, updates the nodes along the way and looks for the best node to put the point on (using a [[Category utility| category utility function]]).
* [[C2ICM(incremental clustering)|C2ICM]]:<ref>{{cite journal | first = F. | last = Can | title = Incremental Clustering for Dynamic Information Processing | journal = ACM Transactions on Information Systems | volume = 11 | issue = 2 | date = 1993 | pages = 143–164 | doi=10.1145/130226.134466| s2cid = 1691726 }}</ref> builds a flat partitioning clustering structure by selecting some objects as cluster seeds/initiators and a non-seed is assigned to the seed that provides the highest coverage, addition of new objects can introduce new seeds and falsify some existing old seeds, during incremental clustering new objects and the members of the falsified clusters are assigned to one of the existing new/old seeds.
* [[CluStream (data clustering)|CluStream]]:<ref>{{cite journal |last1=Aggarwal |first1=Charu C. |last2=Yu |first2=Philip S. |last3=Han |first3=Jiawei |last4=Wang |first4=Jianyong |title=A Framework for Clustering Evolving Data Streams |journal=Proceedings 2003 VLDB Conference |date=2003 |pages=81–92 |doi=10.1016/B978-012722442-8/50016-1 |isbn=9780127224428 |s2cid=2354576 |url=http://www.vldb.org/conf/2003/papers/S04P02.pdf |ref=CluStream}}</ref> uses micro-clusters that are temporal extensions of [[BIRCH]]<ref name="birch" /> cluster feature vector, so that it can decide if a micro-cluster can be newly created, merged or forgotten based in the analysis of the squared and linear sum of the current micro-clusters data-points and timestamps, and then at any point in time one can generate macro-clusters by clustering these micro-clustering using an offline clustering algorithm like [[K-Means]], thus producing a final clustering result.
== References ==
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