Pandas新列从几列的groupby返回max的查找

Question

我有一个数据帧，我正在尝试使用RESULT，Set和Subset列上的groupby生成Subsubset列。我尝试在perc上返回idmax。

| Set | Subset | Subsubset | Class | perc | RESULT |
|-----|--------|-----------|-------|------|--------|
|   1 | A      |         1 | good  |  100 | good   |
|   1 | A      |           | ok    |    0 | good   |
|   1 | A      |           | poor  |    0 | good   |
|   1 | A      |           | bad   |    0 | good   |
|   1 | A      |         2 | good  |   20 | bad    |
|   1 | A      |           | ok    |   10 | bad    |
|   1 | A      |           | poor  |   20 | bad    |
|   1 | A      |           | bad   |   50 | bad    |
|   1 | A      |         3 | good  |    0 | poor   |
|   1 | A      |           | ok    |   10 | poor   |
|   1 | A      |           | poor  |   80 | poor   |
|   1 | A      |           | bad   |   10 | poor   |
|   1 | B      |         1 | good  |   50 | good   |
|   1 | B      |           | ok    |    0 | good   |
|   1 | B      |           | poor  |    1 | good   |
|   1 | B      |           | bad   |   49 | good   |
|   1 | B      |         2 | good  |   60 | good   |
|   1 | B      |           | ok    |   10 | good   |
|   1 | B      |           | poor  |   20 | good   |
|   1 | B      |           | bad   |   10 | good   |

为了澄清，结果将始终是单个值（例如，永远不会看到50/50分割）。

设置数百个子集中的数字，直到ZZ（非常长的表）。

这与类似的问题Python : Getting the Row which has the max value in groups using groupby不同，因为我有兴趣查看MULTIPLE列的分组。

Answer 1

既然你提到了idxmax，那么我们使用idxmax

idx=df.groupby(['Set','Subset','Subsubset'])['perc'].transform('idxmax')

df['RESULT']=df.loc[idx,'Class'].values#df.Class.reindex(idx).values