K-Means算法Python实现
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from numpy import * from random import _inst import numpy as np import matplotlib.pyplot as plt def fileMat(filename): file = open(filename, "r") contain = file.readlines() count = len(contain) features = zeros((count, len(contain[0].split(‘,‘)) - 1)) labels = [] index = 0 for lines in contain: line = lines.strip() listForm = line.split(",") features[index:] = listForm[0:len(listForm) - 1] labels.append(listForm[-1]) index += 1 return labels, features ‘‘‘初始化聚类中心,随机取3个样本点‘‘‘ def initCentroids(dataSet, K): # 初始化k个质心,随机获取 #在dataSet中任取K个向量作为初始的中心向量 return _inst.sample(dataSet, K) ‘‘‘样本点与每个聚类中心的距离‘‘‘ def ouShi(point1, point2): distance = np.sqrt(np.sum(np.square(point1 - point2))) return distance ‘‘‘计算样本中心点‘‘‘ def getMean(clusterDict): centerSet = list() for key in clusterDict.keys(): centerSet.append(np.mean(np.array(clusterDict[key]), axis=0)) # 簇中样本的平均值 return centerSet # 返回的是簇中心的列表 ‘‘‘聚类‘‘‘ def cluster(dataSet, centerSet): clusterDict = dict() for item in dataSet: flag = 0 minDistance = float("inf") for i in range(len(centerSet)): distance = ouShi(item, centerSet[i]) if distance < minDistance: minDistance = distance flag = i#第i类 if flag not in clusterDict.keys(): clusterDict[flag] = list() clusterDict[flag].append(item) return clusterDict ‘‘‘计算平方误差,是根据簇中样本点与该簇中心点的欧氏距离的平方计算的‘‘‘ def getE(clusterDic): sum = 0.0 for key in clusterDic.keys(): distance = 0.0 centerDistance = np.mean(clusterDic[key]) for item in clusterDic[key]: dis = np.square(ouShi(item, centerDistance)) distance += dis sum += distance return sum def showCluster(centerSet, clusterDict): # 展示聚类结果 colorMark = [‘or‘, ‘ob‘, ‘og‘, ‘ok‘, ‘oy‘, ‘ow‘] # 不同簇类的标记 ‘or‘ --> ‘o‘代表圆,‘r‘代表red,‘b‘:blue centroidMark = [‘dr‘, ‘db‘, ‘dg‘, ‘dk‘, ‘dy‘, ‘dw‘] # 质心标记 同上‘d‘代表棱形 for key in clusterDict.keys(): plt.plot(centerSet[key][0], centerSet[key][1], centroidMark[key], markersize=12) # 画质心点 for item in clusterDict[key]: plt.plot(item[0], item[1], colorMark[key]) # 画簇类下的点 plt.show() if __name__ == ‘__main__‘: dataLabels, dataSet = fileMat("TestData.txt") firstCenterSet = initCentroids(list(dataSet), 4) print(‘初始聚类中心为:‘, firstCenterSet) clusterDict = cluster(dataSet, firstCenterSet) newE = getE(clusterDict) oldE = -0.0001 print("------------------------------------ 第1次迭代 ------------------------------------") for key in clusterDict.keys(): buff = list() for i in range(len(clusterDict[key])): buff.append(list(clusterDict[key][i])) print(key, ‘ --> ‘, buff) newCenterSet = list() for i in range(len(firstCenterSet)): newCenterSet.append(list(firstCenterSet[i])) print(‘k个均值向量: ‘, newCenterSet) print(‘平均均方误差: ‘, newE) showCluster(firstCenterSet, clusterDict) d = 2 while abs(newE - oldE) != 0: # 当连续两次聚类结果小于0.0001时,迭代结束 centerSet = getMean(clusterDict) # 获得新的质心 clusterDict = cluster(dataSet, centerSet) # 新的聚类结果 oldE = newE newE = getE(clusterDict) print(‘------------------------------------------- 第%d次迭代 -------------------------------------------‘ % d) for key in clusterDict.keys(): buff = list() for i in range(len(clusterDict[key])): buff.append(list(clusterDict[key][i])) print(key, ‘ --> ‘, buff) newCenterSet = list() for i in range(len(firstCenterSet)): newCenterSet.append(list(firstCenterSet[i])) print(‘k个均值向量: ‘, newCenterSet) print(‘平均均方误差: ‘, newE) showCluster(centerSet, clusterDict) d += 1
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