聚类属于无监督学习，K-means算法是很典型的基于距离的聚类算法，采用距离作为相似性的评价指标，即认为两个对象的距离越近，其相似度就越大。该算法认为簇是由距离靠近的对象组成的，因此把得到紧凑且独立的簇作为最终目标。
下面来看看python实现k-means算法的详细代码吧：
# -*- coding:utf-8 -*-
import random
import numpy as np
from matplotlib import pyplot
class K_Means(object):
# k是分组数；tolerance‘中心点误差'；max_iter是迭代次数
def __init__(self, k=2, tolerance=0.0001, max_iter=300):
self.k_ = k
self.tolerance_ = tolerance
self.max_iter_ = max_iter
def fit(self, data):
self.centers_ = {}
for i in range(self.k_):
self.centers_[i] = data[random.randint(0,len(data))]
# print('center', self.centers_)
for i in range(self.max_iter_):
self.clf_ = {} #用于装归属到每个类中的点[k,len(data)]
for i in range(self.k_):
self.clf_[i] = []
# print("质点:",self.centers_)
for feature in data:
distances = [] #装中心点到每个点的距离[k]
for center in self.centers_:
# 欧拉距离
distances.append(np.linalg.norm(feature - self.centers_[center]))
classification = distances.index(min(distances))
self.clf_[classification].append(feature)
# print("分组情况:",self.clf_)
prev_centers = dict(self.centers_)
for c in self.clf_:
self.centers_[c] = np.average(self.clf_[c], axis=0)
# '中心点'是否在误差范围
optimized = True
for center in self.centers_:
org_centers = prev_centers[center]
cur_centers = self.centers_[center]
if np.sum((cur_centers - org_centers) / org_centers * 100.0) > self.tolerance_:
optimized = False
if optimized:
break
def predict(self, p_data):
distances = [np.linalg.norm(p_data - self.centers_[center]) for center in self.centers_]
index = distances.index(min(distances))
return index
if __name__ == '__main__':
x = np.array([[1, 2], [1.5, 1.8], [5, 8], [8, 8], [1, 0.6], [9, 11]])
k_means = K_Means(k=2)
k_means.fit(x)
for center in k_means.centers_:
pyplot.scatter(k_means.centers_[center][0], k_means.centers_[center][1], marker='*', s=150)
for cat in k_means.clf_:
for point in k_means.clf_[cat]:
pyplot.scatter(point[0], point[1], c=('r' if cat == 0 else 'b'))
predict = [[2, 1], [6, 9]]
for feature in predict:
cat = k_means.predict(feature)
pyplot.scatter(feature[0], feature[1], c=('r' if cat == 0 else 'b'), marker='x')
pyplot.show()
