kNN_Code_part1

#!/usr/bin/python3  
# -*- coding: utf-8 -*-
"""
author: Tiebiao Zhang 2021/11/2
"""

import operator
from numpy import array, tile


def createdataset():
    group = array([[1.0, 1.1], [1.0, 1.0], [0, 0], [0, 0.1]])
    labels = ['A', 'A', 'B', 'B']
    return group, labels


def classify0(inx, dataset, labels, k):
    datasetsize = dataset.shape[0]
    diffmat = tile(inx, (datasetsize, 1)) - dataset
    sqdiffmat = diffmat ** 2
    sqdistances = sqdiffmat.sum(axis=1)
    distances = sqdistances ** 0.5
    sorteddistindicies = distances.argsort()  # argsort获得的是sort后的index
    classcount = {}
    for x in range(k):
        voteilabel = labels[sorteddistindicies[x]]
        classcount[voteilabel] = classcount.get(voteilabel, 0) + 1
    sorteddistindicies = sorted(classcount.items(), key=operator.itemgetter(1), reverse=True) # operator.itemgetter(1) 获取对象的第1个域的值 reverse降序
    return sorteddistindicies[0][0]


a, b = createdataset()

print(classify0([0, 0], a, b, 3))