开始之前,导入numpy、pandas包和数据
import numpy as np
import pandas as pd
df= pd.read_csv('train.csv')
2 第二章:数据清洗及特征处理
我们拿到的数据通常是不干净的,所谓的不干净,就是数据中有缺失值,有一些异常点等,需要经过一定的处理才能继续做后面的分析或建模,所以拿到数据的第一步是进行数据清洗,本章我们将学习缺失值、重复值、字符串和数据转换等操作,将数据清洗成可以分析或建模的亚子。
2.1 缺失值观察与处理
我们拿到的数据经常会有很多缺失值,比如我们可以看到Cabin列存在NaN,那其他列还有没有缺失值,这些缺失值要怎么处理呢
2.1.1 任务一:缺失值观察
(1) 请查看每个特征缺失值个数 (2) 请查看Age, Cabin, Embarked列的数据 以上方式都有多种方式,所以大家多多益善
df.info()
df.isnull().sum()
<class 'pandas.core.frame.DataFrame'>
RangeIndex: 891 entries, 0 to 890
Data columns (total 12 columns):
# Column Non-Null Count Dtype
--- ------ -------------- -----
0 PassengerId 891 non-null int64
1 Survived 891 non-null int64
2 Pclass 891 non-null int64
3 Name 891 non-null object
4 Sex 891 non-null object
5 Age 714 non-null float64
6 SibSp 891 non-null int64
7 Parch 891 non-null int64
8 Ticket 891 non-null object
9 Fare 891 non-null float64
10 Cabin 204 non-null object
11 Embarked 889 non-null object
dtypes: float64(2), int64(5), object(5)
memory usage: 83.7+ KB
PassengerId 0
Survived 0
Pclass 0
Name 0
Sex 0
Age 177
SibSp 0
Parch 0
Ticket 0
Fare 0
Cabin 687
Embarked 2
dtype: int64
df[ ['Age', 'Cabin', 'Embarked'] ].head()
| Age | Cabin | Embarked |
---|
0 | 22.0 | NaN | S |
---|
1 | 38.0 | C85 | C |
---|
2 | 26.0 | NaN | S |
---|
3 | 35.0 | C123 | S |
---|
4 | 35.0 | NaN | S |
---|
2.1.2 任务二:对缺失值进行处理
(1)处理缺失值一般有几种思路 1)删除缺失数据 2)补全缺失数据 (2) 请尝试对Age列的数据的缺失值进行处理 fillna()方法,values= {Age:0} 字典方式 df.loc 筛选isnull()的行 (3) 请尝试使用不同的方法直接对整张表的缺失值进行处理 fillna(0)方法,全部补零
df= pd.read_csv('train.csv')
df1 = df.fillna(value={'Age' :0})
df1.isnull().sum()
PassengerId 0
Survived 0
Pclass 0
Name 0
Sex 0
Age 0
SibSp 0
Parch 0
Ticket 0
Fare 0
Cabin 687
Embarked 2
dtype: int64
df= pd.read_csv('train.csv')
df.loc[ df['Age'].isnull(), 'Age'] =0
df.isnull().sum()
PassengerId 0
Survived 0
Pclass 0
Name 0
Sex 0
Age 0
SibSp 0
Parch 0
Ticket 0
Fare 0
Cabin 687
Embarked 2
dtype: int64
df.fillna(0)
| PassengerId | Survived | Pclass | Name | Sex | Age | SibSp | Parch | Ticket | Fare | Cabin | Embarked |
---|
0 | 1 | 0 | 3 | Braund, Mr. Owen Harris | male | 22.0 | 1 | 0 | A/5 21171 | 7.2500 | 0 | S |
---|
1 | 2 | 1 | 1 | Cumings, Mrs. John Bradley (Florence Briggs Th... | female | 38.0 | 1 | 0 | PC 17599 | 71.2833 | C85 | C |
---|
2 | 3 | 1 | 3 | Heikkinen, Miss. Laina | female | 26.0 | 0 | 0 | STON/O2. 3101282 | 7.9250 | 0 | S |
---|
3 | 4 | 1 | 1 | Futrelle, Mrs. Jacques Heath (Lily May Peel) | female | 35.0 | 1 | 0 | 113803 | 53.1000 | C123 | S |
---|
4 | 5 | 0 | 3 | Allen, Mr. William Henry | male | 35.0 | 0 | 0 | 373450 | 8.0500 | 0 | S |
---|
... | ... | ... | ... | ... | ... | ... | ... | ... | ... | ... | ... | ... |
---|
886 | 887 | 0 | 2 | Montvila, Rev. Juozas | male | 27.0 | 0 | 0 | 211536 | 13.0000 | 0 | S |
---|
887 | 888 | 1 | 1 | Graham, Miss. Margaret Edith | female | 19.0 | 0 | 0 | 112053 | 30.0000 | B42 | S |
---|
888 | 889 | 0 | 3 | Johnston, Miss. Catherine Helen "Carrie" | female | 0.0 | 1 | 2 | W./C. 6607 | 23.4500 | 0 | S |
---|
889 | 890 | 1 | 1 | Behr, Mr. Karl Howell | male | 26.0 | 0 | 0 | 111369 | 30.0000 | C148 | C |
---|
890 | 891 | 0 | 3 | Dooley, Mr. Patrick | male | 32.0 | 0 | 0 | 370376 | 7.7500 | 0 | Q |
---|
891 rows × 12 columns
df= pd.read_csv('train.csv')
df.isnull().sum()
PassengerId 0
Survived 0
Pclass 0
Name 0
Sex 0
Age 177
SibSp 0
Parch 0
Ticket 0
Fare 0
Cabin 687
Embarked 2
dtype: int64
df= pd.read_csv('train.csv')
df_nan= df.dropna(how ='all', subset=['Age'])
df_nan.describe()
| PassengerId | Survived | Pclass | Age | SibSp | Parch | Fare |
---|
count | 714.000000 | 714.000000 | 714.000000 | 714.000000 | 714.000000 | 714.000000 | 714.000000 |
---|
mean | 448.582633 | 0.406162 | 2.236695 | 29.699118 | 0.512605 | 0.431373 | 34.694514 |
---|
std | 259.119524 | 0.491460 | 0.838250 | 14.526497 | 0.929783 | 0.853289 | 52.918930 |
---|
min | 1.000000 | 0.000000 | 1.000000 | 0.420000 | 0.000000 | 0.000000 | 0.000000 |
---|
25% | 222.250000 | 0.000000 | 1.000000 | 20.125000 | 0.000000 | 0.000000 | 8.050000 |
---|
50% | 445.000000 | 0.000000 | 2.000000 | 28.000000 | 0.000000 | 0.000000 | 15.741700 |
---|
75% | 677.750000 | 1.000000 | 3.000000 | 38.000000 | 1.000000 | 1.000000 | 33.375000 |
---|
max | 891.000000 | 1.000000 | 3.000000 | 80.000000 | 5.000000 | 6.000000 | 512.329200 |
---|
【思考1】dropna和fillna有哪些参数,分别如何使用呢?
【思考】检索空缺值用np.nan ,None 以及.isnull() 哪个更好,这是为什么?如果其中某个方式无法找到缺失值,原因又是为什么?
【参考】https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.dropna.html
【参考】https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.fillna.html
2.2 重复值观察与处理
由于这样那样的原因,数据中会不会存在重复值呢,如果存在要怎样处理呢
2.2.1 任务一:请查看数据中的重复值
df= pd.read_csv('train.csv')
df.describe()
df[df.duplicated()]
my_data=np.array( [1,2,3, 1,2,3, 4,5,6, 2,3,4]).reshape(4,3)
my_df= pd.DataFrame( data=my_data, dtype='float64', index=['a', 'b','c','d'],columns=['A', 'B', 'C'])
my_df.head()
my_df[my_df.duplicated()]
#### 2.2.2 任务二:对重复值进行处理
(1)重复值有哪些处理方式呢?
(2)处理我们数据的重复值
方法多多益善
以下是对整个行有重复值的清理的方法举例:
```python
df = df.drop_duplicates()
df.head()
| PassengerId | Survived | Pclass | Name | Sex | Age | SibSp | Parch | Ticket | Fare | Cabin | Embarked |
---|
0 | 1 | 0 | 3 | Braund, Mr. Owen Harris | male | 22.0 | 1 | 0 | A/5 21171 | 7.2500 | NaN | S |
---|
1 | 2 | 1 | 1 | Cumings, Mrs. John Bradley (Florence Briggs Th... | female | 38.0 | 1 | 0 | PC 17599 | 71.2833 | C85 | C |
---|
2 | 3 | 1 | 3 | Heikkinen, Miss. Laina | female | 26.0 | 0 | 0 | STON/O2. 3101282 | 7.9250 | NaN | S |
---|
3 | 4 | 1 | 1 | Futrelle, Mrs. Jacques Heath (Lily May Peel) | female | 35.0 | 1 | 0 | 113803 | 53.1000 | C123 | S |
---|
4 | 5 | 0 | 3 | Allen, Mr. William Henry | male | 35.0 | 0 | 0 | 373450 | 8.0500 | NaN | S |
---|
2.2.3 任务三:将前面清洗的数据保存为csv格式
df.to_csv('test_clear.csv')
2.3 特征观察与处理
我们对特征进行一下观察,可以把特征大概分为两大类: 数值型特征:Survived ,Pclass, Age ,SibSp, Parch, Fare,其中Survived, Pclass为离散型数值特征,Age,SibSp, Parch, Fare为连续型数值特征 文本型特征:Name, Sex, Cabin,Embarked, Ticket,其中Sex, Cabin, Embarked, Ticket为类别型文本特征。
数值型特征一般可以直接用于模型的训练,但有时候为了模型的稳定性及鲁棒性会对连续变量进行离散化。文本型特征往往需要转换成数值型特征才能用于建模分析。
2.3.1 任务一:对年龄进行分箱(离散化)处理
(1) 分箱操作是什么?
(2) 将连续变量Age平均分箱成5个年龄段,并分别用类别变量12345表示
(3) 将连续变量Age划分为(0,5] (5,15] (15,30] (30,50] (50,80]五个年龄段,并分别用类别变量12345表示
(4) 将连续变量Age按10% 30% 50% 70% 90%五个年龄段,并用分类变量12345表示
(5) 将上面的获得的数据分别进行保存,保存为csv格式
df['AgeBand'] = pd.cut(df['Age'], 5,labels = [1,2,3,4,5])
df.head()
| PassengerId | Survived | Pclass | Name | Sex | Age | SibSp | Parch | Ticket | Fare | Cabin | Embarked | AgeBand |
---|
0 | 1 | 0 | 3 | Braund, Mr. Owen Harris | male | 22.0 | 1 | 0 | A/5 21171 | 7.2500 | NaN | S | 2 |
---|
1 | 2 | 1 | 1 | Cumings, Mrs. John Bradley (Florence Briggs Th... | female | 38.0 | 1 | 0 | PC 17599 | 71.2833 | C85 | C | 3 |
---|
2 | 3 | 1 | 3 | Heikkinen, Miss. Laina | female | 26.0 | 0 | 0 | STON/O2. 3101282 | 7.9250 | NaN | S | 2 |
---|
3 | 4 | 1 | 1 | Futrelle, Mrs. Jacques Heath (Lily May Peel) | female | 35.0 | 1 | 0 | 113803 | 53.1000 | C123 | S | 3 |
---|
4 | 5 | 0 | 3 | Allen, Mr. William Henry | male | 35.0 | 0 | 0 | 373450 | 8.0500 | NaN | S | 3 |
---|
df.to_csv('test_ave.csv')
df['AgeBand'] = pd.cut(df['Age'],[0,5,15,30,50,80],labels = [1,2,3,4,5])
df.head(3)
| PassengerId | Survived | Pclass | Name | Sex | Age | SibSp | Parch | Ticket | Fare | Cabin | Embarked | AgeBand |
---|
0 | 1 | 0 | 3 | Braund, Mr. Owen Harris | male | 22.0 | 1 | 0 | A/5 21171 | 7.2500 | NaN | S | 3 |
---|
1 | 2 | 1 | 1 | Cumings, Mrs. John Bradley (Florence Briggs Th... | female | 38.0 | 1 | 0 | PC 17599 | 71.2833 | C85 | C | 4 |
---|
2 | 3 | 1 | 3 | Heikkinen, Miss. Laina | female | 26.0 | 0 | 0 | STON/O2. 3101282 | 7.9250 | NaN | S | 3 |
---|
df.to_csv('test_cut.csv')
df['AgeBand'] = pd.qcut(df['Age'],[0,0.1,0.3,0.5,0.7,0.9],labels = [1,2,3,4,5])
df.head()
| PassengerId | Survived | Pclass | Name | Sex | Age | SibSp | Parch | Ticket | Fare | Cabin | Embarked | AgeBand |
---|
0 | 1 | 0 | 3 | Braund, Mr. Owen Harris | male | 22.0 | 1 | 0 | A/5 21171 | 7.2500 | NaN | S | 2 |
---|
1 | 2 | 1 | 1 | Cumings, Mrs. John Bradley (Florence Briggs Th... | female | 38.0 | 1 | 0 | PC 17599 | 71.2833 | C85 | C | 5 |
---|
2 | 3 | 1 | 3 | Heikkinen, Miss. Laina | female | 26.0 | 0 | 0 | STON/O2. 3101282 | 7.9250 | NaN | S | 3 |
---|
3 | 4 | 1 | 1 | Futrelle, Mrs. Jacques Heath (Lily May Peel) | female | 35.0 | 1 | 0 | 113803 | 53.1000 | C123 | S | 4 |
---|
4 | 5 | 0 | 3 | Allen, Mr. William Henry | male | 35.0 | 0 | 0 | 373450 | 8.0500 | NaN | S | 4 |
---|
df.to_csv('test_pr.csv')
【参考】https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.cut.html
【参考】https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.qcut.html
2.3.2 任务二:对文本变量进行转换
(1) 查看文本变量名及种类 (2) 将文本变量Sex, Cabin ,Embarked用数值变量12345表示 (3) 将文本变量Sex, Cabin, Embarked用one-hot编码表示
方法多多益善
df['Sex'].value_counts()
male 453
female 261
0 1
Name: Sex, dtype: int64
df['Cabin'].value_counts()
G6 4
C23 C25 C27 4
B96 B98 4
F33 3
C22 C26 3
..
D37 1
C92 1
E58 1
E77 1
B4 1
Name: Cabin, Length: 135, dtype: int64
df['Embarked'].value_counts()
S 554
C 130
Q 28
0 1
Name: Embarked, dtype: int64
df['Sex'].unique()
array(['male', 'female', 0], dtype=object)
df['Sex'].nunique()
3
df['Sex_num'] = df['Sex'].replace(['male','female'],[1,2])
df.head()
| PassengerId | Survived | Pclass | Name | Sex | Age | SibSp | Parch | Ticket | Fare | Cabin | Embarked | AgeBand | Sex_num |
---|
0 | 1 | 0 | 3 | Braund, Mr. Owen Harris | male | 22.0 | 1 | 0 | A/5 21171 | 7.2500 | NaN | S | 2 | 1 |
---|
1 | 2 | 1 | 1 | Cumings, Mrs. John Bradley (Florence Briggs Th... | female | 38.0 | 1 | 0 | PC 17599 | 71.2833 | C85 | C | 5 | 2 |
---|
2 | 3 | 1 | 3 | Heikkinen, Miss. Laina | female | 26.0 | 0 | 0 | STON/O2. 3101282 | 7.9250 | NaN | S | 3 | 2 |
---|
3 | 4 | 1 | 1 | Futrelle, Mrs. Jacques Heath (Lily May Peel) | female | 35.0 | 1 | 0 | 113803 | 53.1000 | C123 | S | 4 | 2 |
---|
4 | 5 | 0 | 3 | Allen, Mr. William Henry | male | 35.0 | 0 | 0 | 373450 | 8.0500 | NaN | S | 4 | 1 |
---|
df['Sex_num'] = df['Sex'].map({'male': 1, 'female': 2})
df.head()
| PassengerId | Survived | Pclass | Name | Sex | Age | SibSp | Parch | Ticket | Fare | Cabin | Embarked | AgeBand | Sex_num |
---|
0 | 1 | 0 | 3 | Braund, Mr. Owen Harris | male | 22.0 | 1 | 0 | A/5 21171 | 7.2500 | NaN | S | 2 | 1.0 |
---|
1 | 2 | 1 | 1 | Cumings, Mrs. John Bradley (Florence Briggs Th... | female | 38.0 | 1 | 0 | PC 17599 | 71.2833 | C85 | C | 5 | 2.0 |
---|
2 | 3 | 1 | 3 | Heikkinen, Miss. Laina | female | 26.0 | 0 | 0 | STON/O2. 3101282 | 7.9250 | NaN | S | 3 | 2.0 |
---|
3 | 4 | 1 | 1 | Futrelle, Mrs. Jacques Heath (Lily May Peel) | female | 35.0 | 1 | 0 | 113803 | 53.1000 | C123 | S | 4 | 2.0 |
---|
4 | 5 | 0 | 3 | Allen, Mr. William Henry | male | 35.0 | 0 | 0 | 373450 | 8.0500 | NaN | S | 4 | 1.0 |
---|
from sklearn.preprocessing import LabelEncoder
for feat in ['Cabin', 'Ticket']:
lbl = LabelEncoder()
label_dict = dict(zip(df[feat].unique(), range(df[feat].nunique())))
df[feat + "_labelEncode"] = df[feat].map(label_dict)
df[feat + "_labelEncode"] = lbl.fit_transform(df[feat].astype(str))
df.head()
| PassengerId | Survived | Pclass | Name | Sex | Age | SibSp | Parch | Ticket | Fare | Cabin | Embarked | AgeBand | Sex_num | Cabin_labelEncode | Ticket_labelEncode |
---|
0 | 1 | 0 | 3 | Braund, Mr. Owen Harris | male | 22.0 | 1 | 0 | A/5 21171 | 7.2500 | NaN | S | 2 | 1.0 | 135 | 409 |
---|
1 | 2 | 1 | 1 | Cumings, Mrs. John Bradley (Florence Briggs Th... | female | 38.0 | 1 | 0 | PC 17599 | 71.2833 | C85 | C | 5 | 2.0 | 74 | 472 |
---|
2 | 3 | 1 | 3 | Heikkinen, Miss. Laina | female | 26.0 | 0 | 0 | STON/O2. 3101282 | 7.9250 | NaN | S | 3 | 2.0 | 135 | 533 |
---|
3 | 4 | 1 | 1 | Futrelle, Mrs. Jacques Heath (Lily May Peel) | female | 35.0 | 1 | 0 | 113803 | 53.1000 | C123 | S | 4 | 2.0 | 50 | 41 |
---|
4 | 5 | 0 | 3 | Allen, Mr. William Henry | male | 35.0 | 0 | 0 | 373450 | 8.0500 | NaN | S | 4 | 1.0 | 135 | 374 |
---|
for feat in ["Age", "Embarked"]:
x = pd.get_dummies(df[feat], prefix=feat)
df = pd.concat([df, x], axis=1)
df.head()
| PassengerId | Survived | Pclass | Name | Sex | Age | SibSp | Parch | Ticket | Fare | ... | Age_66.0 | Age_70.0 | Age_70.5 | Age_71.0 | Age_74.0 | Age_80.0 | Embarked_0 | Embarked_C | Embarked_Q | Embarked_S |
---|
0 | 1 | 0 | 3 | Braund, Mr. Owen Harris | male | 22.0 | 1 | 0 | A/5 21171 | 7.2500 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
---|
1 | 2 | 1 | 1 | Cumings, Mrs. John Bradley (Florence Briggs Th... | female | 38.0 | 1 | 0 | PC 17599 | 71.2833 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 |
---|
2 | 3 | 1 | 3 | Heikkinen, Miss. Laina | female | 26.0 | 0 | 0 | STON/O2. 3101282 | 7.9250 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
---|
3 | 4 | 1 | 1 | Futrelle, Mrs. Jacques Heath (Lily May Peel) | female | 35.0 | 1 | 0 | 113803 | 53.1000 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
---|
4 | 5 | 0 | 3 | Allen, Mr. William Henry | male | 35.0 | 0 | 0 | 373450 | 8.0500 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
---|
5 rows × 109 columns
2.3.3 任务三(附加):从纯文本Name特征里提取出Titles的特征(所谓的Titles就是Mr,Miss,Mrs等)
df['Title'] = df.Name.str.extract('([A-Za-z]+)\.', expand=False)
df.head()
| PassengerId | Survived | Pclass | Name | Sex | Age | SibSp | Parch | Ticket | Fare | ... | Age_66.0 | Age_70.0 | Age_70.5 | Age_71.0 | Age_74.0 | Age_80.0 | Embarked_C | Embarked_Q | Embarked_S | Title |
---|
0 | 1 | 0 | 3 | Braund, Mr. Owen Harris | male | 22.0 | 1 | 0 | A/5 21171 | 7.2500 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | Mr |
---|
1 | 2 | 1 | 1 | Cumings, Mrs. John Bradley (Florence Briggs Th... | female | 38.0 | 1 | 0 | PC 17599 | 71.2833 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | Mrs |
---|
2 | 3 | 1 | 3 | Heikkinen, Miss. Laina | female | 26.0 | 0 | 0 | STON/O2. 3101282 | 7.9250 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | Miss |
---|
3 | 4 | 1 | 1 | Futrelle, Mrs. Jacques Heath (Lily May Peel) | female | 35.0 | 1 | 0 | 113803 | 53.1000 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | Mrs |
---|
4 | 5 | 0 | 3 | Allen, Mr. William Henry | male | 35.0 | 0 | 0 | 373450 | 8.0500 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | Mr |
---|
5 rows × 108 columns
df.to_csv('test_fin.csv')
参考资料
[1] hands-on-data-analysis.
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