技術標籤：pandaspython

目錄

• 5.1長寬表的變形
• • 5.1.1 pivot
  • 5.1.2 pivot_table
  • 5.1.3 melt
  • 5.1.4 wide_to_long

5.1長寬表的變形

import pandas as pd 
pd.DataFrame({'Gender':['F','F','M','M']
             ,'Height':[163,160,175,180]})

pd.DataFrame({'Height:F':[163,160],
             'Height:M'
 
:[175,180]})

5.1.1 pivot

df = pd.DataFrame({'Class':[1,1,2,2],
                  'Name':['zhangsan','zhangsan','lisi','lisi']
                  ,'Subject':['Chinese','Math','Chinese','Math']
                  ,'Grade':[80,75,90,85]})
df

df.pivot(index = 'Name',columns = 'Subject',values = 'Grade')

5.1.2 pivot_table

df = pd.DataFrame({'Name':['San Zhang', 'San Zhang', 
                              'San Zhang', 'San Zhang',
                              'Si Li'
 
, 'Si Li', 'Si Li', 'Si Li'],
                   'Subject':['Chinese', 'Chinese', 'Math', 'Math',
                                 'Chinese', 'Chinese', 'Math', 'Math'],
                   'Grade':[80, 90, 100, 90, 70, 80, 85, 95]})
df

df.pivot_table(index = 'Name',
               columns = 'Subject',
               values = 'Grade',
               aggfunc = 'mean')

df.pivot_table(index = 'Name',
               columns = 'Subject',
               values = 'Grade',
               aggfunc = lambda x:x.mean())

df.pivot_table(index = 'Name',
               columns = 'Subject',
               values = 'Grade',
               aggfunc='mean',
               margins=True)

5.1.3 melt

df = pd.DataFrame({'Class':[1,2],
                  'Name':['zhangsan','lisi'],
                  'Chinese':[80,90]
                  ,'Math':[80,75]})

df

df_melted = df.melt(id_vars = ['Class','Name'],
                   value_vars = ['Chinese','Math'],
                   var_name = 'Subject',
                   value_name = 'Grade')
df_melted

5.1.4 wide_to_long

df = pd.DataFrame({'Class':[1,2],'Name':['San Zhang', 'Si Li'],
                   'Chinese_Mid':[80, 75], 'Math_Mid':[90, 85],
                   'Chinese_Final':[80, 75], 'Math_Final':[90, 85]})

df

pd.wide_to_long(df,
                stubnames=['Chinese', 'Math'],
                i = ['Class', 'Name'],
                j='Examination',
                sep='_',
                suffix='.+')