分类 kNN

#coding=utf-8
__author__ = 'sun'
from numpy import *
import operator
dataSet=array([[1.0,1.1],[1.0,1.0],[0,0],[0,0.1]])
labels=['A','A','B','B']
def classify0(inX,dataSet,labels,k):
    dataSetSize=dataSet.shape[0]
    diffMat=tile(inX,(dataSetSize,1))-dataSet#两个矩阵相减
    sqDiffMat=diffMat**2
    sqDistances=sqDiffMat.sum(axis=1)
    distances=sqDistances**0.5
    sortedDistIndicies=distances.argsort()
    classCount={}

    for i in range(k):
        voteIlabel=labels[sortedDistIndicies[i]]
        classCount[voteIlabel]=classCount.get(voteIlabel,0)+1
    sortedClassCount=sorted(classCount.iteritems(),
                            key=operator.itemgetter(1),reverse=True)
    return sortedClassCount[0][0]

result=classify0([0.3,0.3],dataSet,labels,2)
print result