当列匹配时,从另一个数据帧中减去数据帧

我想你需要 GroupBy.transform mean 对于 Series 与原版尺寸相同 DataFrame ,因此可以将列减去 Series.sub :

s = self.data_train.groupby('userId')['rating'].transform('mean')
self.data_train['new'] = self.data_train['rating'].sub(s)

样品 userId 为了更好的样品

print (data_train)
       userId  movieId  rating   timestamp
65414     466      608     4.0   945139883
79720     466     6218     4.0  1089518106
63354     457     4007     3.5  1471383787
29923     466    59333     2.5  1462636955
63651     457   102194     2.5  1471383710

s = data_train.groupby('userId')['rating'].transform('mean')
print (s)
65414    3.5
79720    3.5
63354    3.0
29923    3.5
63651    3.0
Name: rating, dtype: float64

data_train['new'] = data_train['rating'].sub(s)
print (data_train)
       userId  movieId  rating   timestamp  new
65414     466      608     4.0   945139883  0.5
79720     466     6218     4.0  1089518106  0.5
63354     457     4007     3.5  1471383787  0.5
29923     466    59333     2.5  1462636955 -1.0
63651     457   102194     2.5  1471383710 -0.5