輸入數據格式

25 52 164 240 274 328 368 448 538 561 630 687 730 775 825 834

39 120 124 205 401 581 704 814 825 834

35 249 674 712 733 759 854 950

39 422 449 704 825 857 895 937 954 964

15 229 262 283 294 352 381 708 738 766 853 883 966 978

具體函數解釋

1. createC1(dataSet)

創建候選1項集，各item及其support存儲在字典中

def createC1(dataSet):

C1_dict = {} # 物品清單

C1 = []

for items in dataSet:

for item in items:

if item in C1_dict:

C1_dict[item] += 1.; #數字當字典的key

else:

C1_dict[item] = 1.;

for key in C1_dict:

C1.append([key])

print("C1: ",C1)

return C1 #list(C1.keys()) 相等于 list(map(frozenset,C1))

# C1 = createC1(dataSet)

# print("C1:",C1) # C1: [[25], [52], [164], [240], [274]]

2. selectLk(dataSet,Ck,minSupport)

尋找k-頻繁項集

def selectLk(dataSet,Ck,minSupport): #dataSet 原始數據集

scan = {} #字典：存候選項集及其支持度

for tid in dataSet:

# print("tid:",tid) # tid: [33, 217, 283, 346, 496, 515, 626]

for item in Ck: # item: [29] [1,2]

if set(item).issubset(tid): # 轉換list to set 判斷是否為原數據集各tid的子集

item = list(map(str, item))

item = ','.join(item)

if item not in scan.keys():

scan[item] = 1

else:

scan[item] += 1

numItems = float(len(dataSet))

# retList = [] # 頻繁項集

Lk = {}

supportData = {} # 候選項集(ssCnt)的支持度的字典

for key in scan:

support = scan[key] / numItems

#supportData[key] = support

if support >= minSupport:

Lk[key] = support;

# return retList,supportData #retList -> Lk L1: {'368': 0.08, '120': 0.056}

return Lk

3. createCk(Lk,k)

創建k+1-候選項集

def createCk(Lk,k): # Lk:包含k項的頻繁項集

Ck = []

Lk = list(Lk.keys())

print("Lk:",Lk) # Lk: ['368', '120', '283', '766', '529', '217', '177', '354', '684', '829', '460', '438']

lenLk = len(Lk)

for i in range(lenLk):

for j in range(i+1,lenLk):

#前k-2個項相同時，將兩個集合合并

L1 = Lk[i].split(',') # str to list[str]

L1 = list(map(int, L1)) #list[str] to list[int]

L1pre = (L1)[:k-2]

L1pre.sort();

L2 = Lk[j].split(',')

L2 = list(map(int, L2))

L2pre = (L2)[:k-2]

L2pre.sort()

if L1pre == L2pre:

Ck.append(list(set(L1).union(set(L2))))

print("Ck: ",Ck)

return Ck

def apriori(dataSet,minSupport):

C1 = createC1(dataSet);

L1 = selectLk(dataSet,C1,minSupport) #L1 是字典

L = [L1]

k = 2

while(len(L[k-2]) > 0):

Ck = createCk(L[k-2],k)

Lk= selectLk(dataSet,Ck,minSupport)

L.append(Lk)

k += 1

return L

from pprint import pprint

dataSet = loadDataSet() #原始數據集轉換為二維list格式

L = apriori(dataSet,0.01)

pprint(L)

4. 將頻繁項集存入Excel

# write list[dictionary] to an excel file

workbook = xlsxwriter.Workbook('out.xlsx')

worksheet = workbook.add_worksheet()

row = 0

col = 0

worksheet.write(row, col, "Itemset")

worksheet.write(row, col+1, "Support")

for items in L:

for key in items.keys():

row += 1

worksheet.write(row, col, key)

worksheet.write(row, col + 1, items[key])

workbook.close()

總結

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