Python：摘要和聚合DataFrame中的组和子组

问题描述

我正在尝试建立一个表，该表具有按子组划分的组，每个子组具有计数和平均值。例如，我要转换以下数据框：

I am trying to build a table that has groups that are divided by subgroups with count and average for each subgroup. For example, I want to convert the following data frame:

对于这样的表，其中 interval 是一个更大的组，而 a thru i 列成为该组内的子组，每个单元格中都有对应的子组的计数和平均值：

To a table that looks like this where the interval is a bigger group and columns a thru i become subgroups within the group with the corresponding subgroups' count and average in each cell:

我尝试了此尝试，但没有成功：

I have tried this with no success:

推荐答案

使用与和具有新列名称的聚合函数的元组：

Use DataFrame.melt with GroupBy.agg and tuples for aggregate functions with new columns names:

df1 = (df.melt('interval', var_name='source')
         .groupby(['interval','source'])['value']
         .agg([('cnt','count'), ('average','mean')])
         .reset_index())
print (df1.head())
  interval source  cnt  average
0        0      a    1      5.0
1        0      b    1      0.0
2        0      c    1      0.0
3        0      d    1      0.0
4        0      f    1      0.0

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