pandas模块学习第三篇——缺失值处理

1.缺失值处理。

 

inplace参数为True则取代当前df，否则返回一个执行函数的df的复制。

2.但是nan填充值具体是什么呢，可以根据现有的数据经过计算来选择，更符合当前数据的规律。

iloc，即index locate 用index索引进行定位，所以参数是整型，如：df.iloc[10:20, 3:5]
loc，则可以使用column名和index名进行定位，如：
df.loc[‘image1’:‘image10’, ‘age’:‘score’]

pct_change函数计算变化率：（后一个值-前一个值）／前一个值
默认period为1

 

3.层次索引

import numpy as np
import pandas as pd
from pandas import Series,DataFrame
 
#3.pandas层次索引
data = Series([998.4,6455,5432,9765,5432],
              index=[["2001","2001","2001","2002","2002"],
              ["苹果","香蕉","西瓜","苹果","西瓜"]]
              )
print(data)
 
df4 = DataFrame({
    "year":[2001,2001,2002,2002,2003],
    "fruit":["apple","banana","apple","banana","apple"],
    "production":[2345,5632,3245,6432,4532],
    "profits":[245.6,432.7,534.1,354,467.8]
})
 
print(df4)
print("=======层次化索引=======")
df4 = df4.set_index(["year","fruit"])
print(df4)
print("=======依照索引取值=======")
print(df4.ix[2002,"apple"])
print("=======依照层次化索引统计数据=======")
print(df4.sum(level="year"))
print(df4.mean(level="fruit"))
print(df4.min(level=["year","fruit"]))
 
#运行结果：
2001  苹果     998.4
      香蕉    6455.0
      西瓜    5432.0
2002  苹果    9765.0
      西瓜    5432.0
dtype: float64
    fruit  production  profits  year
0   apple        2345    245.6  2001
1  banana        5632    432.7  2001
2   apple        3245    534.1  2002
3  banana        6432    354.0  2002
4   apple        4532    467.8  2003
=======层次化索引=======
             production  profits
year fruit                      
2001 apple         2345    245.6
     banana        5632    432.7
2002 apple         3245    534.1
     banana        6432    354.0
2003 apple         4532    467.8
=======依照索引取值=======
production    3245.0
profits        534.1
Name: (2002, apple), dtype: float64
=======依照层次化索引统计数据=======
      production  profits
year                     
2001        7977    678.3
2002        9677    888.1
2003        4532    467.8
        production     profits
fruit                         
apple         3374  415.833333
banana        6032  393.350000
             production  profits
year fruit                      
2001 apple         2345    245.6
     banana        5632    432.7
2002 apple         3245    534.1
     banana        6432    354.0
2003 apple         4532    467.8

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原文链接：https://blog.youkuaiyun.com/loveliuzz/article/details/78498121