Pandas新列返回从多个列的groupby中查找最大值

Question

我有一个这样的数据帧，我正在尝试生成RESULT列，在Set、Subset和Subsubset列上使用groupby。我尝试在perc上返回idmax。你知道吗

| 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，结果总是一个值（例如，永远不会看到50/50分割）。你知道吗

以百为单位设置数字，子集最多为ZZ（非常长的表格）。你知道吗

这与类似的问题Python : Getting the Row which has the max value in groups using groupby不同，因为在这里我感兴趣的是在多个列上分组。你知道吗

Answer 1

既然您提到了idxmax，那么我们就使用idxmax

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

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