pandas - SKLearn MinMaxScaler - 仅缩放特定列

Question

我想使用 MinMaxScaler 缩放 Pandas 数据帧中的一些（但不是全部）列。我该怎么做？

Answer 1

演示：

In [90]: df = pd.DataFrame(np.random.randn(5, 3), index=list('abcde'), columns=list('xyz'))

In [91]: df
Out[91]:
          x         y         z
a -0.325882 -0.299432 -0.182373
b -0.833546 -0.472082  1.158938
c -0.328513 -0.664035  0.789414
d -0.031630 -1.040802 -1.553518
e  0.813328  0.076450  0.022122

In [92]: from sklearn.preprocessing import MinMaxScaler

In [93]: mms = MinMaxScaler()

In [94]: df[['x','z']] = mms.fit_transform(df[['x','z']])

In [95]: df
Out[95]:
          x         y         z
a  0.308259 -0.299432  0.505500
b  0.000000 -0.472082  1.000000
c  0.306662 -0.664035  0.863768
d  0.486932 -1.040802  0.000000
e  1.000000  0.076450  0.580891

使用以下方法也可以实现相同的结果sklearn.preprocessing.minmax_scale：

from sklearn.preprocessing import minmax_scale

df[['x','z']] = minmax_scale(df[['x','z']])

Answer 2

由于 sklearn >= 0.20，您可以使用Column Transformer

standard_transformer = Pipeline(steps=[
        ('standard', StandardScaler())])

minmax_transformer = Pipeline(steps=[
        ('minmax', MinMaxScaler())])


preprocessor = ColumnTransformer(
        remainder='passthrough', #passthough features not listed
        transformers=[
            ('std', standard_transformer , ['z']),
            ('mm', minmax_transformer , ['x','y'])
        ])