数据清洗之缺失值处理

缺乏、安全感 2023-05-21 13:53 69阅读 0赞

# 缺失值处理 #

*  缺失值首先需要根据实际情况定义
 *  可以采取直接删除法
 *  有时候需要使用替换法或者插值法
 *  常用的替换法有均值替换、前向、后向替换和常数替换

import pandas as pd
    import numpy as np
    import os

os.getcwd()

'D:\\Jupyter\\notebook\\Python数据清洗实战\\数据清洗之数据预处理'

os.chdir('D:\\Jupyter\\notebook\\Python数据清洗实战\\数据')

df = pd.read_csv('MotorcycleData.csv', encoding='gbk', na_values='Na')

def f(x):
        if '$' in str(x):
            x = str(x).strip('$')
            x = str(x).replace(',', '')
        else:
            x = str(x).replace(',', '')
        return float(x)

df['Price'] = df['Price'].apply(f)

df['Mileage'] = df['Mileage'].apply(f)

# 计算缺失比例
    df.apply(lambda x: sum(x.isnull())/len(x), axis=0)

Condition         0.000000
    Condition_Desc    0.778994
    Price             0.000000
    Location          0.000267
    Model_Year        0.000534
    Mileage           0.003470
    Exterior_Color    0.095422
    Make              0.000534
    Warranty          0.318297
    Model             0.016415
    Sub_Model         0.676231
    Type              0.197785
    Vehicle_Title     0.964233
    OBO               0.008808
    Feedback_Perc     0.117710
    Watch_Count       0.530629
    N_Reviews         0.000801
    Seller_Status     0.083411
    Vehicle_Tile      0.007207
    Auction           0.002269
    Buy_Now           0.031630
    Bid_Count         0.707727
    dtype: float64

df.head(3)

3 rows × 22 columns

# how = 'all', 只有当前行都是缺失值才删除
    # how = 'any', 只要当前行有一个缺失值就删除
    df.dropna(how = 'any', axis=0)

0 rows × 22 columns

# subset 根据指定字段判断
    # df.dropna(how='any', subset=['Condition', 'Price', 'Mileage'])

# 缺失值使用0填补
    df.fillna(0).head(5)

<table> 
 <thead> 
  <tr> 
   <th></th> 
   <th>Condition</th> 
   <th>Condition_Desc</th> 
   <th>Price</th> 
   <th>Location</th> 
   <th>Model_Year</th> 
   <th>Mileage</th> 
   <th>Exterior_Color</th> 
   <th>Make</th> 
   <th>Warranty</th> 
   <th>Model</th> 
   <th>...</th> 
   <th>Vehicle_Title</th> 
   <th>OBO</th> 
   <th>Feedback_Perc</th> 
   <th>Watch_Count</th> 
   <th>N_Reviews</th> 
   <th>Seller_Status</th> 
   <th>Vehicle_Tile</th> 
   <th>Auction</th> 
   <th>Buy_Now</th> 
   <th>Bid_Count</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <th>0</th> 
   <td>Used</td> 
   <td>mint!!! very low miles</td> 
   <td>11412.0</td> 
   <td>McHenry, Illinois, United States</td> 
   <td>2013.0</td> 
   <td>16000.0</td> 
   <td>Black</td> 
   <td>Harley-Davidson</td> 
   <td>Unspecified</td> 
   <td>Touring</td> 
   <td>...</td> 
   <td>0</td> 
   <td>FALSE</td> 
   <td>8.1</td> 
   <td>0</td> 
   <td>2427</td> 
   <td>Private Seller</td> 
   <td>Clear</td> 
   <td>True</td> 
   <td>FALSE</td> 
   <td>28.0</td> 
  </tr> 
  <tr> 
   <th>1</th> 
   <td>Used</td> 
   <td>Perfect condition</td> 
   <td>17200.0</td> 
   <td>Fort Recovery, Ohio, United States</td> 
   <td>2016.0</td> 
   <td>60.0</td> 
   <td>Black</td> 
   <td>Harley-Davidson</td> 
   <td>Vehicle has an existing warranty</td> 
   <td>Touring</td> 
   <td>...</td> 
   <td>0</td> 
   <td>FALSE</td> 
   <td>100</td> 
   <td>17</td> 
   <td>657</td> 
   <td>Private Seller</td> 
   <td>Clear</td> 
   <td>True</td> 
   <td>TRUE</td> 
   <td>0.0</td> 
  </tr> 
  <tr> 
   <th>2</th> 
   <td>Used</td> 
   <td>0</td> 
   <td>3872.0</td> 
   <td>Chicago, Illinois, United States</td> 
   <td>1970.0</td> 
   <td>25763.0</td> 
   <td>Silver/Blue</td> 
   <td>BMW</td> 
   <td>Vehicle does NOT have an existing warranty</td> 
   <td>R-Series</td> 
   <td>...</td> 
   <td>0</td> 
   <td>FALSE</td> 
   <td>100</td> 
   <td>0</td> 
   <td>136</td> 
   <td>0</td> 
   <td>Clear</td> 
   <td>True</td> 
   <td>FALSE</td> 
   <td>26.0</td> 
  </tr> 
  <tr> 
   <th>3</th> 
   <td>Used</td> 
   <td>CLEAN TITLE READY TO RIDE HOME</td> 
   <td>6575.0</td> 
   <td>Green Bay, Wisconsin, United States</td> 
   <td>2009.0</td> 
   <td>33142.0</td> 
   <td>Red</td> 
   <td>Harley-Davidson</td> 
   <td>0</td> 
   <td>Touring</td> 
   <td>...</td> 
   <td>0</td> 
   <td>FALSE</td> 
   <td>100</td> 
   <td>0</td> 
   <td>2920</td> 
   <td>Dealer</td> 
   <td>Clear</td> 
   <td>True</td> 
   <td>FALSE</td> 
   <td>11.0</td> 
  </tr> 
  <tr> 
   <th>4</th> 
   <td>Used</td> 
   <td>0</td> 
   <td>10000.0</td> 
   <td>West Bend, Wisconsin, United States</td> 
   <td>2012.0</td> 
   <td>17800.0</td> 
   <td>Blue</td> 
   <td>Harley-Davidson</td> 
   <td>NO WARRANTY</td> 
   <td>Touring</td> 
   <td>...</td> 
   <td>0</td> 
   <td>FALSE</td> 
   <td>100</td> 
   <td>13</td> 
   <td>271</td> 
   <td>OWNER</td> 
   <td>Clear</td> 
   <td>True</td> 
   <td>TRUE</td> 
   <td>0.0</td> 
  </tr> 
 </tbody> 
</table>

5 rows × 22 columns

# 针对一个变量进行缺失值判断，使用其均值进行填补
    df.Mileage.fillna(df.Mileage.mean()).head(5)

0    16000.0
    1       60.0
    2    25763.0
    3    33142.0
    4    17800.0
    Name: Mileage, dtype: float64

df.columns

Index(['Condition', 'Condition_Desc', 'Price', 'Location', 'Model_Year',
           'Mileage', 'Exterior_Color', 'Make', 'Warranty', 'Model', 'Sub_Model',
           'Type', 'Vehicle_Title', 'OBO', 'Feedback_Perc', 'Watch_Count',
           'N_Reviews', 'Seller_Status', 'Vehicle_Tile', 'Auction', 'Buy_Now',
           'Bid_Count'],
          dtype='object')

df[df['Exterior_Color'].isnull()].head(5)

<table> 
 <thead> 
  <tr> 
   <th></th> 
   <th>Condition</th> 
   <th>Condition_Desc</th> 
   <th>Price</th> 
   <th>Location</th> 
   <th>Model_Year</th> 
   <th>Mileage</th> 
   <th>Exterior_Color</th> 
   <th>Make</th> 
   <th>Warranty</th> 
   <th>Model</th> 
   <th>...</th> 
   <th>Vehicle_Title</th> 
   <th>OBO</th> 
   <th>Feedback_Perc</th> 
   <th>Watch_Count</th> 
   <th>N_Reviews</th> 
   <th>Seller_Status</th> 
   <th>Vehicle_Tile</th> 
   <th>Auction</th> 
   <th>Buy_Now</th> 
   <th>Bid_Count</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <th>14</th> 
   <td>Used</td> 
   <td>NaN</td> 
   <td>5500.0</td> 
   <td>Davenport, Iowa, United States</td> 
   <td>2008.0</td> 
   <td>22102.0</td> 
   <td>NaN</td> 
   <td>Harley-Davidson</td> 
   <td>Vehicle does NOT have an existing warranty</td> 
   <td>Touring</td> 
   <td>...</td> 
   <td>NaN</td> 
   <td>FALSE</td> 
   <td>9.3</td> 
   <td>NaN</td> 
   <td>244</td> 
   <td>Private Seller</td> 
   <td>Clear</td> 
   <td>True</td> 
   <td>FALSE</td> 
   <td>16.0</td> 
  </tr> 
  <tr> 
   <th>35</th> 
   <td>Used</td> 
   <td>NaN</td> 
   <td>7700.0</td> 
   <td>Roselle, Illinois, United States</td> 
   <td>2007.0</td> 
   <td>10893.0</td> 
   <td>NaN</td> 
   <td>Harley-Davidson</td> 
   <td>NaN</td> 
   <td>Other</td> 
   <td>...</td> 
   <td>NaN</td> 
   <td>FALSE</td> 
   <td>100</td> 
   <td>NaN</td> 
   <td>236</td> 
   <td>NaN</td> 
   <td>Clear</td> 
   <td>False</td> 
   <td>TRUE</td> 
   <td>NaN</td> 
  </tr> 
  <tr> 
   <th>41</th> 
   <td>Used</td> 
   <td>NaN</td> 
   <td>6800.0</td> 
   <td>Hampshire, Illinois, United States</td> 
   <td>2003.0</td> 
   <td>55782.0</td> 
   <td>NaN</td> 
   <td>Harley-Davidson</td> 
   <td>Vehicle does NOT have an existing warranty</td> 
   <td>Softail</td> 
   <td>...</td> 
   <td>NaN</td> 
   <td>TRUE</td> 
   <td>100</td> 
   <td>2&lt;</td> 
   <td>298</td> 
   <td>Private Seller</td> 
   <td>Clear</td> 
   <td>False</td> 
   <td>TRUE</td> 
   <td>NaN</td> 
  </tr> 
  <tr> 
   <th>55</th> 
   <td>Used</td> 
   <td>NaN</td> 
   <td>29500.0</td> 
   <td>Parma, Michigan, United States</td> 
   <td>1950.0</td> 
   <td>8471.0</td> 
   <td>NaN</td> 
   <td>Harley-Davidson</td> 
   <td>NaN</td> 
   <td>Other</td> 
   <td>...</td> 
   <td>NaN</td> 
   <td>TRUE</td> 
   <td>100</td> 
   <td>24</td> 
   <td>216</td> 
   <td>NaN</td> 
   <td>Clear</td> 
   <td>False</td> 
   <td>TRUE</td> 
   <td>NaN</td> 
  </tr> 
  <tr> 
   <th>72</th> 
   <td>Used</td> 
   <td>NaN</td> 
   <td>6500.0</td> 
   <td>Bourbonnais, Illinois, United States</td> 
   <td>1986.0</td> 
   <td>55300.0</td> 
   <td>NaN</td> 
   <td>Harley-Davidson</td> 
   <td>NaN</td> 
   <td>Touring</td> 
   <td>...</td> 
   <td>NaN</td> 
   <td>TRUE</td> 
   <td>100</td> 
   <td>2&lt;</td> 
   <td>1</td> 
   <td>Private Seller</td> 
   <td>Clear</td> 
   <td>False</td> 
   <td>TRUE</td> 
   <td>NaN</td> 
  </tr> 
 </tbody> 
</table>

5 rows × 22 columns

# 求众数
    df['Exterior_Color'].mode()[0]

'Black'

# 缺失用众数填补
    df['Exterior_Color'].fillna(df['Exterior_Color'].mode()[0]).head(5)

0          Black
    1          Black
    2    Silver/Blue
    3            Red
    4           Blue
    Name: Exterior_Color, dtype: object

df['Mileage'].median()

7083.0

# 对不同变量使用不同数据填补
    # 不加inplace=True，不会对原数据生效
    df.fillna(value={ 'Exterior_Color': df['Exterior_Color'].mode()[0], 
                    'Mileage': df['Mileage'].median(),}).head(5)

<table> 
 <thead> 
  <tr> 
   <th></th> 
   <th>Condition</th> 
   <th>Condition_Desc</th> 
   <th>Price</th> 
   <th>Location</th> 
   <th>Model_Year</th> 
   <th>Mileage</th> 
   <th>Exterior_Color</th> 
   <th>Make</th> 
   <th>Warranty</th> 
   <th>Model</th> 
   <th>...</th> 
   <th>Vehicle_Title</th> 
   <th>OBO</th> 
   <th>Feedback_Perc</th> 
   <th>Watch_Count</th> 
   <th>N_Reviews</th> 
   <th>Seller_Status</th> 
   <th>Vehicle_Tile</th> 
   <th>Auction</th> 
   <th>Buy_Now</th> 
   <th>Bid_Count</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <th>0</th> 
   <td>Used</td> 
   <td>mint!!! very low miles</td> 
   <td>11412.0</td> 
   <td>McHenry, Illinois, United States</td> 
   <td>2013.0</td> 
   <td>16000.0</td> 
   <td>Black</td> 
   <td>Harley-Davidson</td> 
   <td>Unspecified</td> 
   <td>Touring</td> 
   <td>...</td> 
   <td>NaN</td> 
   <td>FALSE</td> 
   <td>8.1</td> 
   <td>NaN</td> 
   <td>2427</td> 
   <td>Private Seller</td> 
   <td>Clear</td> 
   <td>True</td> 
   <td>FALSE</td> 
   <td>28.0</td> 
  </tr> 
  <tr> 
   <th>1</th> 
   <td>Used</td> 
   <td>Perfect condition</td> 
   <td>17200.0</td> 
   <td>Fort Recovery, Ohio, United States</td> 
   <td>2016.0</td> 
   <td>60.0</td> 
   <td>Black</td> 
   <td>Harley-Davidson</td> 
   <td>Vehicle has an existing warranty</td> 
   <td>Touring</td> 
   <td>...</td> 
   <td>NaN</td> 
   <td>FALSE</td> 
   <td>100</td> 
   <td>17</td> 
   <td>657</td> 
   <td>Private Seller</td> 
   <td>Clear</td> 
   <td>True</td> 
   <td>TRUE</td> 
   <td>0.0</td> 
  </tr> 
  <tr> 
   <th>2</th> 
   <td>Used</td> 
   <td>NaN</td> 
   <td>3872.0</td> 
   <td>Chicago, Illinois, United States</td> 
   <td>1970.0</td> 
   <td>25763.0</td> 
   <td>Silver/Blue</td> 
   <td>BMW</td> 
   <td>Vehicle does NOT have an existing warranty</td> 
   <td>R-Series</td> 
   <td>...</td> 
   <td>NaN</td> 
   <td>FALSE</td> 
   <td>100</td> 
   <td>NaN</td> 
   <td>136</td> 
   <td>NaN</td> 
   <td>Clear</td> 
   <td>True</td> 
   <td>FALSE</td> 
   <td>26.0</td> 
  </tr> 
  <tr> 
   <th>3</th> 
   <td>Used</td> 
   <td>CLEAN TITLE READY TO RIDE HOME</td> 
   <td>6575.0</td> 
   <td>Green Bay, Wisconsin, United States</td> 
   <td>2009.0</td> 
   <td>33142.0</td> 
   <td>Red</td> 
   <td>Harley-Davidson</td> 
   <td>NaN</td> 
   <td>Touring</td> 
   <td>...</td> 
   <td>NaN</td> 
   <td>FALSE</td> 
   <td>100</td> 
   <td>NaN</td> 
   <td>2920</td> 
   <td>Dealer</td> 
   <td>Clear</td> 
   <td>True</td> 
   <td>FALSE</td> 
   <td>11.0</td> 
  </tr> 
  <tr> 
   <th>4</th> 
   <td>Used</td> 
   <td>NaN</td> 
   <td>10000.0</td> 
   <td>West Bend, Wisconsin, United States</td> 
   <td>2012.0</td> 
   <td>17800.0</td> 
   <td>Blue</td> 
   <td>Harley-Davidson</td> 
   <td>NO WARRANTY</td> 
   <td>Touring</td> 
   <td>...</td> 
   <td>NaN</td> 
   <td>FALSE</td> 
   <td>100</td> 
   <td>13</td> 
   <td>271</td> 
   <td>OWNER</td> 
   <td>Clear</td> 
   <td>True</td> 
   <td>TRUE</td> 
   <td>0.0</td> 
  </tr> 
 </tbody> 
</table>

5 rows × 22 columns

# 前向填补
    df['Exterior_Color'].fillna(method='ffill').tail(10)

7483      Purple
    7484      Purple
    7485       Black
    7486       Black
    7487        Gray
    7488       Black
    7489       Black
    7490         Red
    7491    TWO TONE
    7492        Gray
    Name: Exterior_Color, dtype: object

# 后向填补
    df['Exterior_Color'].fillna(method='bfill').tail(10)

7483      Purple
    7484       Black
    7485       Black
    7486       Black
    7487        Gray
    7488       Black
    7489       Black
    7490         Red
    7491    TWO TONE
    7492        Gray
    Name: Exterior_Color, dtype: object