【原创】利用python实现apriori关联算法并分析挖掘数据

# -*- coding: utf-8 -*-
import json

# Aprior算法

def loadDataSet():
    '''创建一个用于测试的简单的数据集'''
    test_app=[]
    phone_app = json.load(open("phone_app.json"))
    for item in phone_app.keys():
        for item_son in phone_app[item].keys():
            test_app.append(phone_app[item][item_son])
    return test_app


def createC1(dataSet):
    '''
    构建初始候选项集的列表，即所有候选项集只包含一个元素，
    C1是大小为1的所有候选项集的集合
    '''
    C1 = []
    for transaction in dataSet:
        for item in transaction:
            if [item] not in C1:
                C1.append([item])
    C1.sort()
    return map(frozenset, C1)


def scanD(D, Ck, minSupport):
    '''
    计算Ck中的项集在数据集合D(记录或者transactions)中的支持度,
    返回满足最小支持度的项集的集合，和所有项集支持度信息的字典。
    '''
    ssCnt = {}
    for tid in D:
        for can in Ck:
            if can.issubset(tid):
                ssCnt[can] = ssCnt.get(can, 0) + 1
    numItems = float(len(D))
    retList = []
    supportData = {}
    for key in ssCnt:
        support = ssCnt[key] / numItems
        if support >= minSupport:
            retList.insert(0, key)
        supportData[key] = support
    return retList, supportData

def aprioriGen(Lk, k):
    '''
    由初始候选项集的集合Lk生成新的生成候选项集，
    k表示生成的新项集中所含有的元素个数
    '''
    retList = []
    lenLk = len(Lk)
    for i in range(lenLk):
        for j in range(i + 1, lenLk):
            L1 = list(Lk[i])[: k - 2];
            L2 = list(Lk[j])[: k - 2];
            L1.sort();
            L2.sort()
            if L1 == L2:
                retList.append(Lk[i] | Lk[j])
    return retList


def apriori(dataSet, minSupport=0.5):
    # 构建初始候选项集C1
    C1 = createC1(dataSet)

    D = map(set, dataSet)
    L1, suppData = scanD(D, C1, minSupport)
    L = [L1]
    k = 2

    while (len(L[k - 2]) > 0):
        Ck = aprioriGen(L[k - 2], k)
        Lk, supK = scanD(D, Ck, minSupport)

        suppData.update(supK)

        L.append(Lk)

        k += 1
    return L, suppData

if __name__ == '__main__':
    myDat = loadDataSet()
    # 选择频繁项集
    L, suppData = apriori( myDat, 0.4 )
    print u"频繁项集L：", L
    #print u"所有候选项集的支持度信息：", suppData