"""
Python 3.6
Filename: CodeApriori.py
Author: MaggieForest
Blog: https://www.forestspace.top
Date: 2019/9/29
"""
import csv
def load_data_set():
"""
Load a sample data set (From Data Mining: Concepts and Techniques, 3th Edition)
Returns:
A data set: A list of transactions. Each transaction contains several items.
"""
filename = 'C:\Users\zoushulin\Desktop\Groceries_dataset\Groceries.csv'
with open(filename)as f:
f_csv = csv.reader(f)
for index, val in enumerate(f_csv):
if index != 0:
subList = str(val[1]).replace('}','').replace('{','').split(',')
data_set.append(list(subList))
return data_set
def create_C1(data_set):
"""
Create frequent candidate 1-itemset C1 by scaning data set.
Args:
data_set: A list of transactions. Each transaction contains several items.
Returns:
C1: 包含所有候选一层频繁项集的集合
"""
C1 = set() # 不重复集
for t in data_set:
for item in t:
item_set = frozenset([item]) # item的不可变集合
C1.add(item_set)
print("总项数:" + str(len(C1)))
return C1
def is_apriori(Ck_item, Lksub1):
"""
Judge whether a frequent candidate k-itemset satisfy Apriori property.
Args:
Ck_item: a frequent candidate k-itemset in Ck which contains all frequent
candidate k-itemsets.
Lksub1: Lk-1, a set which contains all frequent candidate (k-1)-itemsets.
Returns:
True: satisfying Apriori property.
False: Not satisfying Apriori property.
"""
for item in Ck_item:
sub_Ck = Ck_item - frozenset([item])
if sub_Ck not in Lksub1:
return False
return True
def create_Ck(Lksub1, k):
"""
Create Ck, a set which contains all all frequent candidate k-itemsets
by Lk-1's own connection operation.
Args:
Lksub1: Lk-1, a set which contains all frequent candidate (k-1)-itemsets.
k: the item number of a frequent itemset.
Return:
Ck: a set which contains all all frequent candidate k-itemsets.
"""
Ck = set()
len_Lksub1 = len(Lksub1)
list_Lksub1 = list(Lksub1)
for i in range(len_Lksub1):
for j in range(1, len_Lksub1):
l1 = list(list_Lksub1[i])
l2 = list(list_Lksub1[j])
l1.sort()
l2.sort()
if l1[0:k - 2] == l2[0:k - 2]:
Ck_item = list_Lksub1[i] | list_Lksub1[j]
# pruning
if is_apriori(Ck_item, Lksub1):
Ck.add(Ck_item)
return Ck
def generate_Lk_by_Ck(data_set, Ck, min_support, support_data):
"""
通过ck 执行delete policy 生成频繁项集
Args:
data_set: A list of transactions. Each transaction contains several items.
Ck: 包含所有频繁候选k项集的集合
min_support: The minimum support.
support_data: A dictionary. 键值对，记录频繁项集和其支持度
Returns:
Lk: 包含所有的频繁项集的字典
"""
Lk = []
item_count = {}
for t in data_set: # 遍历所有条目
for item in Ck: # 候选k阶频繁项集循环
if item.issubset(t): # item是否是t的子集 ，并计数存到item_count
if item not in item_count:
item_count[item] = 1
else:
item_count[item] += 1
t_num = float(len(data_set))
for item in item_count:
if (item_count[item] / t_num) >= min_support: # 支持度比较
# print('LK add : ' + str(item))
Lk.append(item)
support_data[item] = item_count[item] / t_num
# print('LK:' + str(Lk))
return Lk # 返回频繁项集
def generate_L(data_set, k, min_support):
"""
生成所有的频繁项集
Args:
data_set: 数据集
k: 频繁项集的最大项数
min_support: 最小支持度
Returns:
L: The list of Lk.
support_data: A dictionary. The key is frequent itemset and the value is support.
"""
support_data = {}
C1 = create_C1(data_set) # 获得一层候选项集
L1 = generate_Lk_by_Ck(data_set, C1, min_support, support_data) # 获得一层频繁项集
print("len-lk:" + str(len(list(L1))) + " L1:" + str(L1))
Lksub1 = L1.copy()
L = []
L.append(Lksub1) # List of List
for i in range(2, k + 1): # 多层频繁项集的获取
Ci = create_Ck(Lksub1, i)
Li = generate_Lk_by_Ck(data_set, Ci, min_support, support_data)
Lksub1 = Li.copy()
L.append(Lksub1)
return L, support_data # L是所有的频繁项集，按照层数保存的List of List，support_data是频繁项集和支持度的键值对
def generate_big_rules(L, support_data, min_conf):
"""
Generate big rules from frequent itemsets.
Args:
L: The list of Lk. 频繁项集 List of List
support_data: A dictionary. The key is frequent itemset and the value is support.
min_conf: Minimal confidence.最小置信度
Returns:
big_rule_list: A list which contains all big rules. Each big rule is represented
as a 3-tuple.
"""
big_rule_list = []
sub_set_list = []
for i in range(0, len(L)): # 遍历频繁项集
for freq_set in L[i]: # 频繁项集
for sub_set in sub_set_list:
if sub_set.issubset(freq_set):
# print("sub_set:" + str(sub_set))
# print("freq_set:" + str(freq_set))
conf = support_data[freq_set] / support_data[freq_set - sub_set] # 支持度计算
big_rule = (freq_set - sub_set, sub_set, conf)
# print("freq_set - sub_set:" + str(freq_set - sub_set))
if conf >= min_conf and big_rule not in big_rule_list:
# print freq_set-sub_set, " => ", sub_set, "conf: ", conf
big_rule_list.append(big_rule)
sub_set_list.append(freq_set)
return big_rule_list
if name == "main":
"""
Test
"""
data_set = load_data_set()
L, support_data = generate_L(data_set, k=3, min_support=0.02) # L是所有的频繁项集，按照阶数保存的List of List，support_data是频繁项集和支持度的键值对，K=3则最高取到三层
big_rules_list = generate_big_rules(L, support_data, min_conf=0.3)
for Lk in L:
print("=" * 50)
# print("***" + str(len(list(Lk))))
print("frequent " + str(len(list(Lk)[0])) + "-itemsets\t\tsupport")
print("=" * 50)
for freq_set in Lk:
print(freq_set, support_data[freq_set])
print()
print("Big Rules")
for item in big_rules_list:
print(item[0], "=>", item[1], "conf: ", item[2])