只对边界点进行adasyn过采样 python代码
时间: 2023-03-14 14:35:08 浏览: 74
我不太了解您说的ada-syn过采样,但我可以为您提供一些python代码,以帮助您实现边界点过采样:from imblearn.over_sampling import ADASYN X_resampled, y_resampled = ADASYN().fit_sample(X, y)
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adasyn过采样代码
下面是一个关于ADASYN过采样的示例代码:
```python
import numpy as np
from collections import Counter
def ADASYN(X, y, k=5, ratio=0.5):
minority_class = Counter(y).most_common()[-1][0]
majority_class = Counter(y).most_common()[0][0]
# 找出少数类样本和多数类样本的索引
minority_indices = np.where(y == minority_class)[0]
majority_indices = np.where(y == majority_class)[0]
# 计算每个少数类样本与其k个近邻样本的距离比例
distances = []
for i in minority_indices:
distances.append(np.sum((X[i] - X[majority_indices])**2, axis=1))
distances = np.array(distances)
# 计算每个少数类样本需要生成的合成样本数量
G = np.sum(distances < np.percentile(distances, ratio * 100, axis=1)[:, np.newaxis], axis=1)
# 生成合成样本
synthetic_samples = []
for i, count in enumerate(G):
if count > 0:
knn_indices = np.argsort(distances[i])[:k]
for j in range(int(count)):
diff = X[majority_indices[knn_indices[j]]] - X[minority_indices[i]]
gap = np.random.random()
synthetic_sample = X[minority_indices[i]] + gap * diff
synthetic_samples.append(synthetic_sample)
# 更新X和y
X = np.concatenate((X, np.array(synthetic_samples)), axis=0)
y = np.concatenate((y, np.array([minority_class] * len(synthetic_samples))), axis=0)
return X, y
```
这段代码实现了ADASYN(Adaptive Synthetic Sampling)过采样方法,用于不平衡数据集中的少数类样本合成。它使用了numpy和collections模块来处理数据和计数操作。函数`ADASYN`接受特征矩阵`X`和标签向量`y`作为输入,同时还可以指定近邻数量`k`和合成样本比例`ratio`。它返回经过过采样后的特征矩阵和标签向量。
注意:这只是一个示例代码,实际使用时可能需要根据数据集的特点进行调整和优化。
ADASYN自适应综合过采样python实现
ADASYN(Adaptive Synthetic Sampling)是一种针对不平衡数据集的过采样方法,它可以根据不同类别之间的分布差异性来生成合成样本。相比于传统的过采样方法,ADASYN可以更好地保留原始数据的特征信息,从而提高分类器的性能。
以下是ADASYN自适应综合过采样的Python实现:
```python
from collections import Counter
import numpy as np
from sklearn.neighbors import NearestNeighbors
def ADASYN(X, y, k=5, ratio=0.5):
"""
ADASYN自适应综合过采样
:param X: 特征矩阵
:param y: 标签矩阵
:param k: 邻居数,默认为5
:param ratio: 合成样本比例,默认为0.5
:return: 合成后的特征矩阵和标签矩阵
"""
# 统计每个类别的样本数
counter = Counter(y)
# 计算少数类样本数目
minority_num = min(counter.values())
# 计算多数类样本数目
majority_num = max(counter.values())
# 计算需要合成的新样本数目
synthetic_num = int((minority_num * ratio) / (1 - ratio))
# 初始化合成后的特征矩阵和标签矩阵
synthetic_X = np.zeros((synthetic_num, X.shape[1]))
synthetic_y = np.zeros(synthetic_num)
# 计算每个少数类样本需要合成的新样本数目
for i, minority_class in enumerate(counter.keys()):
# 获取少数类样本的索引
minority_indices = np.where(y == minority_class)[0]
# 计算每个少数类样本需要合成的新样本数目
if i == 0:
synthetic_minority_num = synthetic_num
else:
synthetic_minority_num = int(synthetic_num * (counter[minority_class] / minority_num))
# 使用K近邻算法生成新样本
knn = NearestNeighbors(n_neighbors=k).fit(X[minority_indices])
for j in range(synthetic_minority_num):
# 随机选择一个少数类样本
index = np.random.randint(0, minority_num)
# 找到该样本的k个近邻
_, neighbors = knn.kneighbors(X[minority_indices[index]].reshape(1, -1))
# 随机选择一个近邻
nn_index = np.random.randint(0, k)
# 计算插值权重
weight = np.random.rand()
# 生成新样本
synthetic_X[j] = X[minority_indices[index]] + weight * (X[minority_indices[neighbors[0][nn_index]]] - X[minority_indices[index]])
synthetic_y[j] = minority_class
# 合并原始样本和新样本
X_resampled = np.vstack((X, synthetic_X))
y_resampled = np.hstack((y, synthetic_y))
return X_resampled, y_resampled
```