用python实现K-means聚类算法

好的，以下是用Python实现K-means聚类算法的代码：

import numpy as np
from sklearn.datasets import make_blobs

def euclidean_distance(x1, x2):
    return np.sqrt(np.sum((x1 - x2)**2))

class KMeans:
    def __init__(self, k=5, max_iters=100, plot_steps=False):
        self.k = k
        self.max_iters = max_iters
        self.plot_steps = plot_steps
        
        # list of sample indices for each cluster
        self.clusters = [[] for _ in range(self.k)]
        # mean feature vector for each cluster
        self.centroids = []
    
    def predict(self, X):
        self.X = X
        self.n_samples, self.n_features = X.shape
        
        # initialize centroids
        random_sample_idxs = np.random.choice(self.n_samples, self.k, replace=False)
        self.centroids = [self.X[idx] for idx in random_sample_idxs]
        
        # optimization loop
        for _ in range(self.max_iters):
            # update clusters
            self.clusters = self._create_clusters(self.centroids)
            if self.plot_steps:
                self.plot()
            
            # update centroids
            centroids_old = self.centroids.copy()
            self.centroids = self._get_centroids(self.clusters)
            
            # check if converged
            if self._is_converged(centroids_old, self.centroids):
                break
            
            if self.plot_steps:
                self.plot()
            
        # return cluster labels
        return self._get_cluster_labels(self.clusters)
    
    def _get_cluster_labels(self, clusters):
        labels = np.empty(self.n_samples)
        for cluster_idx, cluster in enumerate(clusters):
            for sample_idx in cluster:
                labels[sample_idx] = cluster_idx
        return labels
    
    def _create_clusters(self, centroids):
        clusters = [[] for _ in range(self.k)]
        for idx, sample in enumerate(self.X):
            centroid_idx = self._closest_centroid(sample, centroids)
            clusters[centroid_idx].append(idx)
        return clusters
    
    def _closest_centroid(self, sample, centroids):
        distances = [euclidean_distance(sample, point) for point in centroids]
        closest_idx = np.argmin(distances)
        return closest_idx
    
    def _get_centroids(self, clusters):
        centroids = np.zeros((self.k, self.n_features))
        for cluster_idx, cluster in enumerate(clusters):
            cluster_mean = np.mean(self.X[cluster], axis=0)
            centroids[cluster_idx] = cluster_mean
        return centroids
    
    def _is_converged(self, centroids_old, centroids):
        distances = [euclidean_distance(centroids_old[i], centroids[i]) for i in range(self.k)]
        return np.sum(distances) == 0
    
    def plot(self):
        fig, ax = plt.subplots(figsize=(12, 8))

        for i, index in enumerate(self.clusters):
            point = self.X[index].T
            ax.scatter(*point)

        for point in self.centroids:
            ax.scatter(*point, marker="x", color='black', linewidth=2)

        plt.show()

这里我们先定义了一个 `euclidean_distance` 函数来计算两个样本之间的欧几里得距离。然后定义了 `KMeans` 类，其中我们定义了聚类数、最大迭代次数和是否绘制聚类步骤的标志。在 `predict` 方法中进行了优化迭代，首先初始化聚类中心，然后根据聚类中心更新聚类并更新聚类中心，直到算法收敛或达到最大迭代次数。最后返回聚类标签。在 `_create_clusters` 方法中，我们根据每个样本到聚类中心的距离将其分配到相应的聚类中。在 `_get_centroids` 方法中，我们计算每个聚类的平均特征向量，并返回平均特征向量作为聚类中心。在 `_is_converged` 方法中，我们使用欧几里得距离判断算法是否收敛。最后，我们在 `plot` 方法中绘制了每个聚类的数据点和聚类中心。