帮我写一个python实现基于信息熵进行划分选择的决策树算法
时间: 2023-05-18 22:06:02 浏览: 158
当然可以,以下是一个简单的 Python 实现:
```python
import math
def entropy(data):
total = len(data)
counts = {}
for item in data:
if item not in counts:
counts[item] = 0
counts[item] += 1
entropy = 0
for count in counts.values():
p = count / total
entropy -= p * math.log2(p)
return entropy
def split_data(data, attribute):
splits = {}
for item in data:
value = item[attribute]
if value not in splits:
splits[value] = []
splits[value].append(item)
return splits
def decision_tree(data, attributes):
if len(attributes) == 0:
return None
if len(set([item['label'] for item in data])) == 1:
return data[0]['label']
best_attribute = None
best_entropy = None
for attribute in attributes:
splits = split_data(data, attribute)
attribute_entropy = 0
for split in splits.values():
split_entropy = entropy([item['label'] for item in split])
split_weight = len(split) / len(data)
attribute_entropy += split_weight * split_entropy
if best_entropy is None or attribute_entropy < best_entropy:
best_attribute = attribute
best_entropy = attribute_entropy
tree = {best_attribute: {}}
remaining_attributes = [a for a in attributes if a != best_attribute]
splits = split_data(data, best_attribute)
for value, split_data in splits.items():
subtree = decision_tree(split_data, remaining_attributes)
tree[best_attribute][value] = subtree
return tree
```
这个算法使用信息熵来选择最佳的划分属性,然后递归地构建决策树。
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