k-means
Project Address:
dataset in ML/ML_ation/knn
K近邻算法
- 优点:精度高、异常不敏感、无数据输入假定
- 缺点:计算复杂度高、空间复杂度高
- 适用数据:数值型、标称型
- 选择k个最相似数据中次数出现最多的分类,作为新数据的分类
k-means 伪码
- 计算当前点与已知分类点距离
- 按距离递增排序,选取最近的前K个
- 确定前k个点所在类别的出现频率
- 返回出现最高的频率最为当前点的分类返回
python code
def classify0(inX, dataSet,labels, k):
dataSetSize = dataSet.shape[0]
#print(dataSetSize)
diffMat = tile(inX, (dataSetSize,1)) - dataSet
#print(diffMat)
sqDiffMat = diffMat ** 2
sqDistance = sqDiffMat.sum(axis = 1)
#print(sqDistance)
distance = sqDistance ** 0.5
sortedDistanceIndices = distance.argsort()
#print (sortedDistanceIndices)
classCount = {}
for i in range(k):
voteIlabel = labels[sortedDistanceIndices[i]]
classCount[voteIlabel] = classCount.get(voteIlabel,0) + 1
sortedClassCount = sorted(classCount.iteritems(), key = operator.itemgetter(1),
reverse = True)
#print(sortedClassCount)
return sortedClassCount[0][0]
def file2matrix(filename):
fr = open(filename)
numberOfLines = len(fr.readlines()) #get the number of lines in the file
returnMat = zeros((numberOfLines,3)) #prepare matrix to return
classLabelVector = [] #prepare labels return
fr = open(filename)
index = 0
for line in fr.readlines():
line = line.strip()
listFromLine = line.split('\t')
returnMat[index,:] = listFromLine[0:3]
classLabelVector.append(int(listFromLine[-1]))
index += 1
return returnMat,classLabelVector
使用第二列和第三列数据形成散点图
import knn
group, labels = knn.creatdataset()
#print( knn.classify0([0,0],group,labels, 3) )
datingDatMat, datinglabels = knn.file2matrix('datingTestSet2.txt')
import matplotlib
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111)
ax.scatter(datingDatMat[:,1], datingDatMat[:,2])
plt.show()
./test.py
修改,加入颜色
#ax.scatter(datingDatMat[:,1], datingDatMat[:,2])
->>>>>
ax.scatter(datingDatMat[:,1], datingDatMat[:,2],15.0 *array(datinglabels), 15.0 *array(datinglabels))
修改坐标参考,改为使用第一列和第二列数据
#ax.scatter(datingDatMat[:,1], datingDatMat[:,2],15.0 *array(datinglabels), 15.0 *array(datinglabels))
->>>>>>>
ax.scatter(datingDatMat[:,0], datingDatMat[:,1],15.0 *array(datinglabels), 15.0 *array(datinglabels))
数值归一化
newValue = (oldValue - min)/(max - min)
def autoNorm(dataSet):
minVals = dataSet.min(0)
maxVals = dataSet.max(0)
ranges = maxVals - minVals
normDataSet = zeros(shape(dataSet))
m = dataSet.shape[0]
normDataSet = dataSet - tile(minVals,(m,1))
normDataSet = normDataSet/tile(ranges,(m,1))
return normDataSet,ranges, minVals
def datingClassTest():
hoRatio = 0.05
datingDatMat, datinglabels = file2matrix('datingTestSet2.txt')
normSet,ranges, minVals = autoNorm(datingDatMat)
m = normSet.shape[0]
numTestVecs = int(m* hoRatio)
errorCount = 0
for i in range(numTestVecs):
classifierResult = classify0(normSet[i,:],normSet[numTestVecs:m,:],datinglabels[numTestVecs:m],3)
print "the classifier came back with: %d , the real answer is: %d" % (classifierResult, datinglabels[i])
if(classifierResult != datinglabels[i]): errorCount += 1.0
print "the total error rate is %f " % (errorCount/float(numTestVecs))
knn.datingClassTest()
手写字符识别
def img2vector(filename):
returnVect = zeros((1,1024))
fr = open(filename)
for i in range(32):
lineStr = fr.readline()
for j in range(32):
returnVect[0,32*i+j] = int(lineStr[j])
return returnVect
from os import listdir
def handwritingClassTest():
hwLabels = []
trainingFileList = listdir('trainingDigits') #load the training set
m = len(trainingFileList)
trainingMat = zeros((m,1024))
for i in range(m):
fileNameStr = trainingFileList[i]
fileStr = fileNameStr.split('.')[0] #take off .txt
classNumStr = int(fileStr.split('_')[0])
hwLabels.append(classNumStr)
trainingMat[i,:] = img2vector('trainingDigits/%s' % fileNameStr)
testFileList = listdir('testDigits') #iterate through the test set
errorCount = 0.0
mTest = len(testFileList)
for i in range(mTest):
fileNameStr = testFileList[i]
fileStr = fileNameStr.split('.')[0] #take off .txt
classNumStr = int(fileStr.split('_')[0])
vectorUnderTest = img2vector('testDigits/%s' % fileNameStr)
classifierResult = classify0(vectorUnderTest, trainingMat, hwLabels, 3)
print "the classifier came back with: %d, the real answer is: %d" % (classifierResult, classNumStr)
if (classifierResult != classNumStr): errorCount += 1.0
print "\nthe total number of errors is: %d" % errorCount
print "\nthe total error rate is: %f" % (errorCount/float(mTest))
./test.py
#!/usr/bin/python
from numpy import *
import operator
knn.handwritingClassTest()