基于前向贪心策略的属性约简算法python实现
时间: 2023-07-11 22:26:34 浏览: 39
以下是一个基于前向贪心策略的属性约简算法的 Python 实现:
```python
def is_consistent(data, attributes, attribute):
"""
判断属性集 attributes 加上属性 后是否一致
"""
consistent = True
for row in data:
for a in attributes:
if row[a] != row[attribute]:
consistent = False
break
if not consistent:
break
return consistent
def calculate_dependency(data, attributes, attribute):
"""
计算属性集 attributes 对属性 attribute 的依赖度
"""
count_consistent = 0
for row in data:
if is_consistent(data, attributes, attribute):
count_consistent += 1
return count_consistent / len(data)
def forward_greedy(data, threshold):
"""
基于前向贪心策略的属性约简算法
"""
# 初始化属性集和依赖度
attributes = set(data.columns) - {'decision'}
dependency = {}
for attribute in attributes:
dependency[attribute] = calculate_dependency(data, set(), attribute)
# 依次加入属性,直到满足阈值
while True:
max_dependency = max(dependency.values())
if max_dependency >= threshold:
break
for attribute in attributes:
if dependency[attribute] == max_dependency:
attributes.remove(attribute)
if is_consistent(data, attributes, 'decision'):
dependency.pop(attribute)
else:
dependency[attribute] = calculate_dependency(data, attributes, attribute)
return attributes
```
这个算法从所有属性开始,依次加入属性,直到满足给定的依赖度阈值。每次加入属性后,判断属性集是否一致,如果一致则该属性不再参与计算,否则计算其对目标属性的依赖度。最后返回约简后的属性集。