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MyKNN.py
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MyKNN.py
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# -*- coding: utf-8 -*-
"""
Created on Sun Jun 17 20:19:17 2018
定义一个符合sklearn标准的分类器
@author: xhj
"""
from pylab import *
from math import sqrt
from collections import Counter
class kNNClassifier(object):
def __init__(self, k):
self.k = k
self._x_train = None
self._y_train = None
def fit(self, x_train, y_train):
# assert
self._x_train = x_train
self._y_train = y_train
return self
def predict(self, x_predict):
# assert
y_predict = [self._predict(x) for x in x_predict]
return np.array(y_predict)
def _predict(self, x):
x_train = self._x_train
y_train = self._y_train
k = self.k
assert 1<= k <= x_train.shape[0], 'k must be valid'
assert x_train.shape[0] == y_train.shape[0], "train's size must be equal to y'size"
assert x_train.shape[1] == x.shape[0], 'the feature number of x must be right'
distance = np.sqrt(np.sum((X_train-x)**2, axis=1))
nearest = np.argsort(distance)
topK_y = y_train[nearest[:k]]
votes = Counter(topK_y)
return votes.most_common(1)[0][0]