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1.
Online mining of data streams is an important data mining problem with broad applications. However, it is also a difficult
problem since the streaming data possess some inherent characteristics. In this paper, we propose a new single-pass algorithm,
called DSM-FI (data stream mining for frequent itemsets), for online incremental mining of frequent itemsets over a continuous
stream of online transactions. According to the proposed algorithm, each transaction of the stream is projected into a set
of sub-transactions, and these sub-transactions are inserted into a new in-memory summary data structure, called SFI-forest
(summary frequent itemset forest) for maintaining the set of all frequent itemsets embedded in the transaction data stream
generated so far. Finally, the set of all frequent itemsets is determined from the current SFI-forest. Theoretical analysis
and experimental studies show that the proposed DSM-FI algorithm uses stable memory, makes only one pass over an online transactional
data stream, and outperforms the existing algorithms of one-pass mining of frequent itemsets.
相似文献
Suh-Yin LeeEmail: |
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频繁项集挖掘是数据流挖掘中的一个热点问题.提出了一种新的数据流频繁闭项集挖掘算法MFCI-SW.首先设计了两个新的数据结构:频繁闭项集表FCIL和频繁闭合模式树MFCI-SW-Tree,在此基础上以滑动窗口中的基本窗口为更新单位,在每个基本窗口中提取出频繁闭项集的数据项,将其支持度F和窗口序列号K存到FCIL中;然后随着新基本窗口的到来,通过删除频繁闭项集表中K值最小的数据项和插入新数据项完成对FCIL的更新和MFCI-SW-Tree树的裁剪;最后在MFCI-SW-Tree中可以迅速挖掘出满足用户需要的频繁闭项集.实验结果证明了该算法在执行效率上明显优于DS-CFI算法. 相似文献
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挖掘数据流界标窗口Top-K频繁项集 总被引:3,自引:0,他引:3
数据流频繁项集挖掘是目前数据挖掘与知识发现领域的热点研究课题,在许多领域有重要应用.然而支持度阈值的设定需要一定的领域知识,设置不当会给后续的分析处理带来很多困难和不必要的负担,因此挖掘数据流top-K频繁项集有重要意义.提出一个挖掘数据流界标窗口top-K频繁项集的动态增量近似算法TOPSIL-Miner,为此设计了存储流数据摘要信息的概要结构TOPSIL-Tree以及动态记录挖掘相关信息的树层最大支持度表MaxSL、项目序表OIL,TOPSET和最小支持度表MinSL等,并分析了与这些概要结构相关的挖掘特性.在此基础上研究算法的3种优化措施:1)剪枝当前数据流的平凡项集;2)挖掘过程中启发式自适应提升挖掘阈值;3)动态提升剪枝阈值.对算法的误差上界进行了分析研究.最后通过实验验证了算法的可行性、精确性和时空高效性. 相似文献
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对于大型数据,频繁项集挖掘显得庞大而冗余,挖掘最大频繁项集可以减少挖出的频繁项集的个数。可是对于不确定性数据流,传统判断项集是否频繁的方法已不能准确表达项集的频繁性,而且目前还没有在不确定数据流上挖掘最大频繁项集的相关研究。因此,针对上述不足,提出了一种基于衰减模型的不确定性数据流最大频繁项集挖掘算法TUFSMax。该算法采用标记树结点的方法,使得算法不需要超集检测就可挖掘出所有的最大频繁项集,节约了超集检测时间。实验证明了提出的算法在时间和空间上具有高效性。 相似文献
6.
近年来,数据流挖掘一直是国内外研究的热点,频繁项集挖掘又是数据流挖掘中的重要问题。根据数据流无限性和流动性的特点,提出了一种在滑动窗口中挖掘频繁项集的算法FIM-SW,FIM-SW算法主要是采用垂直的数据库表示方法,使用二进制向量表示每个数据项,并利用Apriori性质产生频繁项集。实验结果表明,这种算法显著地提高了挖掘效率。 相似文献
7.
数据流闭频繁项集挖掘算法得到了广泛的研究,其中一个典型的工作就是NewMomen、算法。针对New-
Moment算法存在搜索空间大而造成算法时间效率低的问题,提出了一种改进的数据流闭频繁项集挖掘算法A-Ncw-
Moment。它设计了一个二进制位表示项目与扩展的频繁项目列表相结合的数据结构,来记录数据流信息及闭频繁项
集。在窗体初始阶段,首先挖掘频繁1一项集所产生的支持度为最大的最长闭频繁项集,接着提出新的“不需扩展策略”
和“向下扩展策略”来避免生成大量中间结果,快速发现其余闭频繁项集,达到极大缩小搜索空间的目的。在窗体滑动
阶段,提出“动态不频繁剪枝策略”来从已生成的闭频繁项集中快速删除非闭频繁项集,并提出“动态不搜索策略”来动
态维护所有闭频繁项集的生成,以降低闭频繁项集的维护代价,提高算法的效率。理论分析与实验结果表明,A-New-
Moment算法具有较好的性能。 相似文献
8.
对于不确定性数据,传统判断项集是否频繁的方法并不能准确表达项集的频繁性,同样对于大型数据,频繁项集显得庞大和冗余。针对上述不足,在水平挖掘算法Apriori的基础上,提出一种基于不确定性数据的频繁闭项集挖掘算法UFCIM。利用置信度概率表达项集频繁的准确性,置信度越高,项集为频繁的准确性也越高,且由于频繁闭项集是频繁项集的一种无损压缩表示,因此利用压缩形式的频繁闭项集替代庞大的频繁项集。实验结果表明,该算法能够快速地挖掘出不确定性数据中的频繁闭项集,在减少项集冗余的同时保证项集的准确性和完整性。 相似文献
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基于滑动窗口的数据流闭合频繁模式的挖掘 总被引:12,自引:1,他引:11
频繁闭合模式集惟一确定频繁模式完全集并且数量小得多,然而,如何挖掘滑动窗口中的频繁闭合模式集是一个很大的挑战.根据数据流的特点,提出了一种发现滑动窗口中频繁闭合模式的新方法DS_CFI.DS_CFI算法将滑动窗口分割为若干个基本窗口,以基本窗口为更新单位。利用已有的频繁闭合模式挖掘算法计算每个基本窗口的潜在频繁闭合项集,将它们及其子集存储到一种新的数据结构DSCFI_tree中,DSCFI_tree能够增量更新,利用DSCFI_tree可以快速地挖掘滑动窗口中的所有频繁闭合模式.最后,通过实验验证了这种方法的有效性. 相似文献
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A data stream is a massive, open-ended sequence of data elements continuously generated at a rapid rate. Mining data streams is more difficult than mining static databases because the huge, high-speed and continuous characteristics of streaming data. In this paper, we propose a new one-pass algorithm called DSM-MFI (stands for Data Stream Mining for Maximal Frequent Itemsets), which mines the set of all maximal frequent itemsets in landmark windows over data streams. A new summary data structure called summary frequent itemset forest (abbreviated as SFI-forest) is developed for incremental maintaining the essential information about maximal frequent itemsets embedded in the stream so far. Theoretical analysis and experimental studies show that the proposed algorithm is efficient and scalable for mining the set of all maximal frequent itemsets over the entire history of the data streams. 相似文献
12.
A new concise representation of frequent itemsets using generators and a positive border 总被引:2,自引:2,他引:0
A complete set of frequent itemsets can get undesirably large due to redundancy when the minimum support threshold is low
or when the database is dense. Several concise representations have been previously proposed to eliminate the redundancy.
Generator based representations rely on a negative border to make the representation lossless. However, the number of itemsets
on a negative border sometimes even exceeds the total number of frequent itemsets. In this paper, we propose to use a positive
border together with frequent generators to form a lossless representation. A positive border is usually orders of magnitude
smaller than its corresponding negative border. A set of frequent generators plus its positive border is always no larger
than the corresponding complete set of frequent itemsets, thus it is a true concise representation. The generalized form of
this representation is also proposed. We develop an efficient algorithm, called GrGrowth, to mine generators and positive
borders as well as their generalizations. The GrGrowth algorithm uses the depth-first-search strategy to explore the search
space, which is much more efficient than the breadth-first-search strategy adopted by most of the existing generator mining
algorithms. Our experiment results show that the GrGrowth algorithm is significantly faster than level-wise algorithms for
mining generator based representations, and is comparable to the state-of-the-art algorithms for mining frequent closed itemsets.
相似文献
Guimei LiuEmail: |
13.
针对已有的多数据流协同频繁项集挖掘算法存在内存占用率高以及发现频繁项集效率低的问题,提出了改进的多数据流协同频繁项集挖掘(MCMD-Stream)算法。首先,该算法利用单遍扫描数据库的字节序列滑动窗口挖掘算法发现数据流中的潜在频繁项集和频繁项集;其次,构建类似频繁模式树(FP-Tree)的压缩频繁模式树(CP-Tree)存储已发现的潜在频繁项集和频繁项集,同时更新CP-Tree树中每个节点生成的对数倾斜时间表中的频繁项计数;最后,通过汇总分析得出在多条数据流中多次出现的且有价值的频繁项集,即协同频繁项集。相比A-Stream和H-Stream算法,MCMD-Stream算法不仅能够提高多数据流中协同频繁项集挖掘的效率,并且还降低了内存空间的使用率。实验结果表明MCMD-Stream算法能够有效地应用于多数据流的协同频繁项集挖掘。 相似文献
14.
目前已提出了许多基于Apriori算法思想的频繁项目集挖掘算法,这些算法可以有效地挖掘出事务数据库中的短频繁项目集,但对于长频繁项目集的挖掘而言,其性能将明显下降.为此,提出了一种频繁闭项目集挖掘算法MFCIA,该算法可以有效地挖掘出事务数据库中所有的频繁项目集,并对其更新问题进行了研究,提出了一种相应的频繁闭项目集增量式更新算法UMFCIA,该算法将充分利用先前的挖掘结果来节省发现新的频繁闭项目集的时间开销.实验结果表明算法MFCIA是有效可行的. 相似文献
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由于不确定数据的向下封闭属性,挖掘全部频繁项集的方法会得到一个指数级的结果。为获得一个较小的合适的结果集,研究了在不确定数据上挖掘频繁闭项集,并提出了一种新的频繁闭项集挖掘算法——NA-PFCIM。该算法将项集挖掘过程看作一个概率分布函数,考虑到基于正态分布模型的方法提取的频繁项集精确度较高,而且支持大型数据库,采用了正态分布模型提取频繁项集。同时,为了减少搜索空间以及避免冗余计算,利用基于深度优先搜索的策略来获得所有的概率频繁闭项集。该算法还设计了两个剪枝策略:超集修剪和子集修剪。最后,在常用的数据集(T10I4D100K、Accidents、Mushroom、Chess)上,将提出的NA-PFCIM算法和基于泊松分布的A-PFCIM算法进行比较。实验结果表明,NA-PFCIM算法能够减少所要扩展的项集,同时减少项集频繁概率的计算,其性能优于对比算法。 相似文献
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The purpose of mining frequent itemsets is to identify the items in groups that always appear together and exceed the user-specified threshold of a transaction database. However, numerous frequent itemsets may exist in a transaction database, hindering decision making. Recently, the mining of frequent closed itemsets has become a major research issue because sets of frequent closed itemsets are condensed yet complete representations of frequent itemsets. Therefore, all frequent itemsets can be derived from a group of frequent closed itemsets. Nonetheless, the number of transactions in a transaction database can increase rapidly in a short time period, and a number of the transactions may be outdated. Thus, frequent closed itemsets may be changed with the addition of new transactions or the deletion of old transactions from the transaction database. Updating previously closed itemsets when transactions are added or removed from the transaction database is challenging. This study proposes an efficient algorithm for incrementally mining frequent closed itemsets without scanning the original database. The proposed algorithm updates closed itemsets by performing several operations on the previously closed itemsets and added/deleted transactions without searching the previously closed itemsets. The experimental results show that the proposed algorithm significantly outperforms previous methods, which require a substantial length of time to search previously closed itemsets. 相似文献
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Jianyong Wang Han J. Lu Y. Tzvetkov P. 《Knowledge and Data Engineering, IEEE Transactions on》2005,17(5):652-663
Frequent itemset mining has been studied extensively in literature. Most previous studies require the specification of a min/spl I.bar/support threshold and aim at mining a complete set of frequent itemsets satisfying min/spl I.bar/support. However, in practice, it is difficult for users to provide an appropriate min/spl I.bar/support threshold. In addition, a complete set of frequent itemsets is much less compact than a set of frequent closed itemsets. In this paper, we propose an alternative mining task: mining top-k frequent closed itemsets of length no less than min/spl I.bar/l, where k is the desired number of frequent closed itemsets to be mined, and min/spl I.bar/l is the minimal length of each itemset. An efficient algorithm, called TFP, is developed for mining such itemsets without mins/spl I.bar/support. Starting at min/spl I.bar/support = 0 and by making use of the length constraint and the properties of top-k frequent closed itemsets, min/spl I.bar/support can be raised effectively and FP-Tree can be pruned dynamically both during and after the construction of the tree using our two proposed methods: the closed node count and descendant/spl I.bar/sum. Moreover, mining is further speeded up by employing a top-down and bottom-up combined FP-Tree traversing strategy, a set of search space pruning methods, a fast 2-level hash-indexed result tree, and a novel closed itemset verification scheme. Our extensive performance study shows that TFP has high performance and linear scalability in terms of the database size. 相似文献