如何使用 Group by、Pivo​​t_table、Stack 和 Unstack 重塑 Pandas Dataframe

Question

我有一个如下所示的数据框：

我想将其更改为：

我知道使用 groupby &/或 pivot_table &/or stack 很容易做到这一点 - 我似乎无法摆脱基础。我的笔记并没有很好地告诉我如何做到这一点。我以为我与 pandas 文档中的 pivot_table 很接近——但连一级都做不到——更不用说 2 级了。因为我不想聚合任何东西。我的笔记都在做聚合...

欢迎采纳任何建议

创建第一个数据框的代码：

df2 = pd.DataFrame({'CPC_qtr_root': {13: 0.13493790567404607,
  14: 0.14353736611331172,
  15: 0.10359919568913414,
  16: 0.077153346715340618,
  17: 0.066759430932458397,
  39: 0.12067193385680651,
  40: 0.049033000970486448,
  41: 0.047640864406214359,
  42: 0.040086869604689483,
  43: 0.038795815932666726,
  100: 0.11017683494905577,
  101: 0.15510499735697988,
  102: 0.16478351543691827,
  103: 0.091894700285988867,
  104: 0.0359603120618152},
 'Country': {13: u'Afghanistan',
  14: u'Afghanistan',
  15: u'Afghanistan',
  16: u'Afghanistan',
  17: u'Afghanistan',
  39: u'Albania',
  40: u'Albania',
  41: u'Albania',
  42: u'Albania',
  43: u'Albania',
  100: u'Angola',
  101: u'Angola',
  102: u'Angola',
  103: u'Angola',
  104: u'Angola'},
 'IncomeLevel': {13: 'Lower Income',
  14: 'Lower Income',
  15: 'Lower Income',
  16: 'Lower Income',
  17: 'Lower Income',
  39: 'Upper Middle Income',
  40: 'Upper Middle Income',
  41: 'Upper Middle Income',
  42: 'Upper Middle Income',
  43: 'Upper Middle Income',
  100: 'Lower Middle Income',
  101: 'Lower Middle Income',
  102: 'Lower Middle Income',
  103: 'Lower Middle Income',
  104: 'Lower Middle Income'},
 'Rate': {13: 27.0,
  14: 37.0,
  15: 35.0,
  16: 39.0,
  17: 48.0,
  39: 95.0,
  40: 95.0,
  41: 96.0,
  42: 93.0,
  43: 96.0,
  100: 36.0,
  101: 65.0,
  102: 66.0,
  103: 52.0,
  104: 52.0},
 'Year': {13: 2000,
  14: 2001,
  15: 2002,
  16: 2003,
  17: 2004,
  39: 2000,
  40: 2001,
  41: 2002,
  42: 2003,
  43: 2004,
  100: 2000,
  101: 2001,
  102: 2002,
  103: 2003,
  104: 2004}})

Answer 1

将set_index 与stack 和unstack 一起使用：

df3 = df2.set_index(['Year','Country']).stack().unstack(1)
print (df3)
Country             Afghanistan              Albania               Angola
Year                                                                     
2000 CPC_qtr_root      0.134938             0.120672             0.110177
     IncomeLevel   Lower Income  Upper Middle Income  Lower Middle Income
     Rate                    27                   95                   36
2001 CPC_qtr_root      0.143537             0.049033             0.155105
     IncomeLevel   Lower Income  Upper Middle Income  Lower Middle Income
     Rate                    37                   95                   65
2002 CPC_qtr_root      0.103599            0.0476409             0.164784
     IncomeLevel   Lower Income  Upper Middle Income  Lower Middle Income
     Rate                    35                   96                   66
2003 CPC_qtr_root     0.0771533            0.0400869            0.0918947
     IncomeLevel   Lower Income  Upper Middle Income  Lower Middle Income
     Rate                    39                   93                   52
2004 CPC_qtr_root     0.0667594            0.0387958            0.0359603
     IncomeLevel   Lower Income  Upper Middle Income  Lower Middle Income
     Rate                    48                   96                   52

获取混合类型：

print (df3.head().applymap(type))
Country                Afghanistan          Albania           Angola
Year                                                                
2000 CPC_qtr_root  <class 'float'>  <class 'float'>  <class 'float'>
     IncomeLevel     <class 'str'>    <class 'str'>    <class 'str'>
     Rate          <class 'float'>  <class 'float'>  <class 'float'>
2001 CPC_qtr_root  <class 'float'>  <class 'float'>  <class 'float'>
     IncomeLevel     <class 'str'>    <class 'str'>    <class 'str'>

Answer 2

您可以先将数据框从宽到长融合，使用 Year 和 Country 作为 ID，使用 IncomeLevel、CPC_qtr_root 和 Rate 作为值：

df3 = pd.melt(df2, id_vars=['Year', 'Country'], value_vars=['IncomeLevel', 'CPC_qtr_root', 'Rate'])

然后你可以旋转你的表：

pd.pivot_table(df3, index = ['Year', 'variable'], 
                columns = 'Country',
                values = 'value',
                aggfunc = np.sum,
                fill_value = 0)

这会返回：

Country             Afghanistan              Albania               Angola
Year variable                                                            
2000 CPC_qtr_root      0.134938             0.120672             0.110177
     IncomeLevel   Lower Income  Upper Middle Income  Lower Middle Income
     Rate                    27                   95                   36
2001 CPC_qtr_root      0.143537             0.049033             0.155105
     IncomeLevel   Lower Income  Upper Middle Income  Lower Middle Income
     Rate                    37                   95                   65
2002 CPC_qtr_root      0.103599            0.0476409             0.164784
     IncomeLevel   Lower Income  Upper Middle Income  Lower Middle Income
     Rate                    35                   96                   66
2003 CPC_qtr_root     0.0771533            0.0400869            0.0918947
     IncomeLevel   Lower Income  Upper Middle Income  Lower Middle Income
     Rate                    39                   93                   52
2004 CPC_qtr_root     0.0667594            0.0387958            0.0359603
     IncomeLevel   Lower Income  Upper Middle Income  Lower Middle Income
     Rate                    48                   96                   52