Python手动实现kmeans聚类和调用sklearn实现

1. 算法步骤

1. 随机选取k个样本点充当k个簇的中心点；
2. 计算所有样本点与各个簇中心之间的距离，然后把样本点划入最近的簇中；
3. 根据簇中已有的样本点，重新计算簇中心；
4. 重复步骤2和3，直到簇中心不再改变或改变很小。

2. 手动Python实现

import numpy as np
import matplotlib.pyplot as plt
from sklearn.datasets.samples_generator import make_blobs

n_data = 400
n_cluster = 4
# generate training data
X, y = make_blobs(n_samples=n_data, centers=n_cluster, cluster_std=0.60, random_state=0)

# generate centers of clusters
centers = np.random.rand(4, 2)*5

EPOCH = 10
tol = 1e-5
for epoch in range(EPOCH):
    labels = np.zeros(n_data, dtype=np.int)

    # 计算每个点到簇中心的距离并分配label
    for i in range(n_data):
        distance = np.sum(np.square(X[i]-centers), axis=1)
        label = np.argmin(distance)
        labels[i] = label

    # 重新计算簇中心
    for i in range(n_cluster):
        indices = np.where(labels == i)[0]       # 找出第i簇的样本点的下标
        points = X[indices]
        centers[i, :] = np.mean(points, axis=0)  # 更新第i簇的簇中心

plt.scatter(X[:, 0], X[:, 1], c=labels, s=40, cmap='viridis')
plt.show()

运行结果：(注：当簇中心初始化不好时，可能计算会有点错误)

 

3. 调用sklearn实现kmeans

import matplotlib.pyplot as plt
from sklearn.cluster import KMeans
from sklearn.datasets.samples_generator import make_blobs

# Generate some data
X, y = make_blobs(n_samples=400, centers=4, cluster_std=0.60, random_state=0)

# kmeans clustering
kmeans = KMeans(4, random_state=0)
kmeans.fit(X)   # 训练模型
labels = kmeans.predict(X)   # 预测分类
plt.scatter(X[:, 0], X[:, 1], c=labels, s=40, cmap='viridis')
plt.show()

运行结果：