从头开始的KNN算法

Question

我正试图从头开始执行KNN算法，但是我得到了一个非常奇怪的错误："KeyError: 0“。

我想这意味着我在某个地方有一本空字典，但我不明白这怎么可能。为了清楚起见，我可能会在黑匣子KNN算法中添加数据工作得很好，所以它肯定必须在代码中.

这是我的密码：

import numpy as np
import pandas as pd
import csv
import scipy.stats as stats
import math
from collections import Counter
import operator
from operator import itemgetter


"""Training features dataset"""
filenametrain_data = 'training_data.csv'
training_feature_set = pd.read_csv(filenametrain_data, header=None, usecols=range(1,13627))

"""Training labels dataset"""
filenametrain_label = 'training_labels.csv'
training_feature_label = pd.read_csv(filenametrain_label, header=None, usecols=[1], names=['Category'])

"""Split into training and testing datasets 90%/10%"""
from sklearn.cross_validation import train_test_split
X_train, X_test, y_train, y_test = train_test_split(training_feature_set, training_feature_label, test_size = 0.1, random_state=42)


"""KNN Model"""
def distance(X_train, y_train):
    dist = 0.0
    for i in range(len(X_train)):
        dist += pow((X_train[i] - y_train[i]), 2)
    return math.sqrt(dist)

def getNeighbors(X_train, y_train, X_test, k):
    distances = []
    for i in range(len(X_train)):
        dist = distance(X_test, X_train[i])
        distances.append((X_train[i], dist, y_train[i]))
    distances.sort(key=operator.itemgetter(1))
    neighbor = []
    for elem in range(k):
        neighbor.append((distances[elem][0], distances[elem][2]))
    return neighbor

def getResponse(neighbors):
    classVotes = {}
    for x in range(len(neighbors)):
        response = int(neighbors[x][-1])
        if response in classVotes:
            classVotes[response] += 1
        else:
            classVotes[response] = 1
    sortedVotes = sorted(classVotes.items(), key=operator.itemgetter(1), reverse = True)
    return sortedVotes[0][0]

"""Prediction"""    
predictions = []
k = 4
for x in range(len(X_test)):
    neighbors = getNeighbors(X_train, y_train, y_test[x], k)
    result = getResponse(neighbors)
    predictions.append(result)   

返回的错误是：

回溯(最近一次调用)： 文件""，第2行，在邻居= getNeighbors(X_train，y_train，y_testx，k)中 文件"C:\ANACONDA\lib\site-packages\pandas\core\frame.py"，第1797行，在getitem中返回self._getitem_column(键) 文件"C:\ANACONDA\lib\site-packages\pandas\core\frame.py"，第1804行，_getitem_column返回self._get_item_cache(键) 文件"C:\ANACONDA\lib\site-packages\pandas\core\generic.py"，第1084行，以_get_item_cache值=self._data.get(项目)为单位 文件"C:\ANACONDA\lib\site-packages\pandas\core\internals.py"，第2851行，在get loc = self.items.get_loc(item)中 文件"C:\ANACONDA\lib\site-packages\pandas\core\index.py"，第1572行，在get_loc返回self._engine.get_loc(_values_from_object(key))中 文件"pandas\index.pyx"，第134行，pandas.index.IndexEngine.get_loc (pandas\index.c:3824) 文件"pandas\index.pyx"，第154行，在pandas.index.IndexEngine.get_loc (pandas\index.c:3704)中 文件"pandas\hashtable.pyx"，第686行，pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12280) 文件"pandas\hashtable.pyx"，第694行，pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12231) KeyError: 0

数据集可以访问这里。

Answer 1

编辑:您可能有一个额外的字符在您的csv文件开始。尝试在read_csv()调用中指定编码。参见csv.html中的“编码”

编码: str，默认无编码，用于读/写UTF (例如。‘’utf 8‘)Python标准编码列表：https://docs.python.org/3/library/codecs.html#standard-encodings

当你不需要一个点的时候，你使用的是一个点(在两个地方，我可以从球棒上看到)：

operator.itemgetter(1)

具体而言，您已经导入了项目管理器：

from operator import itemgetter

因此，当您调用itemgetter时，只需调用它而不使用点符号：

itemgetter(1)