将数据框的结果按几列分组，并计算每列不同的唯一值

Question

我有一个具有以下结构的数据框：

Group    Subgroup    Results1       Results2
  A         s1          OK             NOK
  A         s1          OK             OK
  A         s2          NOK            NOK
  A         s2          OK             NOK
  B         s3          OK             Not tested
  B         s3          Not tested     NOK
  B         s4          OK             NOK

我想以某种方式获取每个结果列的计数：

                            Results1                    Results2
                     OK    NOK    Not tested         OK    NOK    Not tested
    A       s1       2     1      0                  1     2      0
    A       s2       1     3      ...                ...   ...    ...
    B       s3       ...   ...    ...                ...   ...    ...
    B       s4       ...   ...    ...                ...   ...    ...

有什么办法可以用熊猫来做到这一点？

Answer 1

将DataFrame.melt与crosstab和DataFrame.rename_axis一起使用以删除列名称：

df = df.melt(['Group','Subgroup'])

df = (pd.crosstab([df['Group'], df['Subgroup']], [df['variable'], df['value']])
        .rename_axis([None, None], axis=1))
print (df)
               Results1               Results2              
                    NOK Not tested OK      NOK Not tested OK
Group Subgroup                                              
A     s1              0          0  2        1          0  1
      s2              1          0  1        2          0  0
B     s3              0          1  1        1          1  0
      s4              0          0  1        1          0  0