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研究生: 張元哲
Yuan-Che Chang
論文名稱: FP-tree(Frequent Pattern Tree)的調整維護技術研究
指導教授: 陳彥良
Yen-Liang Chen
口試委員:
學位類別: 碩士
Master
系所名稱: 管理學院 - 資訊管理學系
Department of Information Management
畢業學年度: 89
語文別: 中文
論文頁數: 51
中文關鍵詞: 資料挖掘
外文關鍵詞: Data Mining, association rules, FP-tree
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  • 然而上述的兩類方法都需要掃描資料庫兩次以上,在超大型的交易資料庫上進行這樣的動作將相當費時,因此如果能夠依照交易資料庫的異動情況,以incremental的方式修改large itemsets來維護association rules的正確性,又不需要重新掃描資料庫,便相當有價值。過去所提出的incremental維護方法,均是針對第(1)類方法所進行的研究,而第(2)類方法目前都還沒有人提出相關的incremental維護方法,本研究便是針對第(2)類方法中的FP-tree結構,提出incremental維護演算法FPI(FP-tree Incremental),可以在資料庫發生insert、delete或update時,不需要重新掃描整個資料庫即可很有效率地動態調整FP-tree,使它維持正確的結構。另外一種常見的情況是產生association rule的minimum support變小時,由於FP-tree並未包含原先minimum support下屬於infrequent item的node,故需要重新掃描資料庫來建構新的FP-tree,FPI在這種情況下也可以達到動態調整的目的,而不用浪費掃描整個資料庫的I/O時間來重新建構FP-tree。
    由於FP-tree通常遠小於交易資料庫本身而可以放在主記憶體中,所以一旦完成FP-tree的建構,以FP-growth來產生frequent patterns就非常的迅速,因此它所花費的主要時間便在掃描資料庫的I/O和建構FP-tree之上,本研究所提供的FPI演算法可以即時地維護FP-tree正確結構,使association rules可以快速產生。


    圖 目 錄 3 表 目 錄 4 1.緒論 5 2.FP-tree的建構方式 8 3.FP-tree的維護架構 12 4.FPI演算法 15 5.FPI的functions 25 5.1 FP-insert function 25 5.2 FP-delete function 28 5.3 FP-move-up function 31 5.4 FP-go-down function 38 6.實驗評估及效率研究 46 6.1 minimum support值向下調整時的比較 46 6.2 deleted and added transactions的個別比較 47 7.結論 49 8.參考文獻 50

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