I1

I2

I3

I4

I5

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6

2

2

class treeNode:

    def __init__(self, nameValue, numOccur, parentNode):

        self.name = nameValue #节点名字

        self.count = numOccur #节点计数值

        self.nodeLink = None #用于链接相似的元素项

        self.parent = parentNode      #needs to be updated

        self.children = {} #子节点

    def inc(self, numOccur):

        '''

        对count变量增加给定值

        '''

        self.count += numOccur

    def disp(self, ind=1):

        '''

        将树以文本形式展示

        '''

        print ('  '*ind, self.name, ' ', self.count)

        for child in self.children.values():

            child.disp(ind+1)

def createTree(dataSet, minSup=1):

    '''

    创建FP树

    '''

    headerTable = {}    #第一次扫描数据集

    for trans in dataSet:#计算item出现频数

        for item in trans:

            headerTable[item] = headerTable.get(item, 0) + dataSet[trans]

    headerTable = {k:v for k,v in headerTable.items() if v >= minSup}

    freqItemSet = set(headerTable.keys())

    #print ('freqItemSet: ',freqItemSet)

    if len(freqItemSet) == 0: return None, None  #如果没有元素项满足要求，则退出

    for k in headerTable:

        headerTable[k] = [headerTable[k], None] #初始化headerTable

    #print ('headerTable: ',headerTable)

    #第二次扫描数据集

    retTree = treeNode('Null Set', 1, None) #创建树

    for tranSet, count in dataSet.items():  

        localD = {}

        for item in tranSet:  #put transaction items in order

            if item in freqItemSet:

                localD[item] = headerTable[item][0]

        if len(localD) > 0:

            orderedItems = [v[0] for v in sorted(localD.items(), key=lambda p: p[1], reverse=True)]

            updateTree(orderedItems, retTree, headerTable, count)#将排序后的item集合填充的树中

    return retTree, headerTable #返回树型结构和头指针表

def updateTree(items, inTree, headerTable, count):

    if items[0] in inTree.children:#检查第一个元素项是否作为子节点存在

        inTree.children[items[0]].inc(count) #存在，更新计数

    else:   #不存在，创建一个新的treeNode,将其作为一个新的子节点加入其中

        inTree.children[items[0]] = treeNode(items[0], count, inTree)

        if headerTable[items[0]][1] == None: #更新头指针表

            headerTable[items[0]][1] = inTree.children[items[0]]

        else:

            updateHeader(headerTable[items[0]][1], inTree.children[items[0]])

    if len(items) > 1:#不断迭代调用自身，每次调用都会删掉列表中的第一个元素

        updateTree(items[1::], inTree.children[items[0]], headerTable, count)

def updateHeader(nodeToTest, targetNode):

    '''

    this version does not use recursion

    Do not use recursion to traverse a linked list!

    更新头指针表，确保节点链接指向树中该元素项的每一个实例

    '''

    while (nodeToTest.nodeLink != None): 

        nodeToTest = nodeToTest.nodeLink

        nodeToTest.nodeLink = targetNode

def ascendTree(leafNode, prefixPath): #迭代上溯整棵树

    if leafNode.parent != None:

        prefixPath.append(leafNode.name)

        ascendTree(leafNode.parent, prefixPath)

def findPrefixPath(basePat, treeNode): #treeNode comes from header table

    condPats = {}

    while treeNode != None:

        prefixPath = []

        ascendTree(treeNode, prefixPath)

        if len(prefixPath) > 1: 

            condPats[frozenset(prefixPath[1:])] = treeNode.count

        treeNode = treeNode.nodeLink

    return condPats

def mineTree(inTree, headerTable, minSup, preFix, freqItemList):

    bigL = [v[0] for v in sorted(headerTable.items(), key=lambda p: p[1][0])]# 1.排序头指针表

    for basePat in bigL:  #从头指针表的底端开始

        newFreqSet = preFix.copy()

        newFreqSet.add(basePat)

        print ('finalFrequent Item: ',newFreqSet)    #添加的频繁项列表

        freqItemList.append(newFreqSet)

        condPattBases = findPrefixPath(basePat, headerTable[basePat][1])

        print ('condPattBases :',basePat, condPattBases)

        # 2.从条件模式基创建条件FP树

        myCondTree, myHead = createTree(condPattBases, minSup)

        #         print ('head from conditional tree: ', myHead)

        if myHead != None: # 3.挖掘条件FP树

            print ('conditional tree for: ',newFreqSet)

            myCondTree.disp(1)

            mineTree(myCondTree, myHead, minSup, newFreqSet, freqItemList)

def loadSimpDat():

    simpDat=[

        ['I1','I2','I5'],

        ['I2','I4'],

        ['I2','I3'],

        ['I1','I2','I4'],

        ['I1','I3'],

        ['I2','I3'],

        ['I1','I3'],

        ['I1','I2','I3','I5'],

        ['I1','I2','I3']

        ]

    return simpDat

def createInitSet(dataSet):

    retDict = {}

    for trans in dataSet:

        retDict[frozenset(trans)] = retDict.get(frozenset(trans), 0) + 1 #若没有相同事项，则为1；若有相同事项，则加1 

    return retDict

minSup=2

simpDat = loadSimpDat()

initSet = createInitSet(simpDat)

myFPtree, myHeaderTab = createTree(initSet, minSup)

myFPtree.disp()

myFreqList = []

mineTree(myFPtree, myHeaderTab, minSup, set([]), myFreqList)