我试图使用scikit-learn的LabelEncoder来编码字符串标签的pandas DataFrame。由于数据帧有许多(50+)列,我想避免为每一列创建一个LabelEncoder对象;我宁愿只有一个大的LabelEncoder对象,它可以跨所有数据列工作。
将整个DataFrame扔到LabelEncoder中会产生以下错误。请记住,我在这里使用的是虚拟数据;实际上,我正在处理大约50列的字符串标记数据,所以需要一个解决方案,不引用任何列的名称。
import pandas
from sklearn import preprocessing
df = pandas.DataFrame({
'pets': ['cat', 'dog', 'cat', 'monkey', 'dog', 'dog'],
'owner': ['Champ', 'Ron', 'Brick', 'Champ', 'Veronica', 'Ron'],
'location': ['San_Diego', 'New_York', 'New_York', 'San_Diego', 'San_Diego',
'New_York']
})
le = preprocessing.LabelEncoder()
le.fit(df)
回溯(最近一次调用):
文件“”,第1行,在
文件"/Users/bbalin/anaconda/lib/python2.7/site-packages/sklearn/预处理/label.py",第103行
y = column_or_1d(y, warn=True)
文件"/Users/bbalin/anaconda/lib/python2.7/site-packages/sklearn/utils/validation.py",第306行,在column_or_1d中
raise ValueError("错误的输入形状{0}".format(形状))
ValueError:错误的输入形状(6,3)
对于如何解决这个问题有什么想法吗?
从scikit-learn 0.20开始,你可以使用sklearn.compose.ColumnTransformer和sklearn.预处理. onehotencoder:
如果你只有分类变量,OneHotEncoder直接:
from sklearn.preprocessing import OneHotEncoder
OneHotEncoder(handle_unknown='ignore').fit_transform(df)
如果你有异构类型的特性:
from sklearn.compose import make_column_transformer
from sklearn.preprocessing import RobustScaler
from sklearn.preprocessing import OneHotEncoder
categorical_columns = ['pets', 'owner', 'location']
numerical_columns = ['age', 'weigth', 'height']
column_trans = make_column_transformer(
(categorical_columns, OneHotEncoder(handle_unknown='ignore'),
(numerical_columns, RobustScaler())
column_trans.fit_transform(df)
文档中有更多选项:http://scikit-learn.org/stable/modules/compose.html#columntransformer-for-heterogeneous-data
根据对@PriceHardman解决方案提出的意见,我将提出以下版本的类:
class LabelEncodingColoumns(BaseEstimator, TransformerMixin):
def __init__(self, cols=None):
pdu._is_cols_input_valid(cols)
self.cols = cols
self.les = {col: LabelEncoder() for col in cols}
self._is_fitted = False
def transform(self, df, **transform_params):
"""
Scaling ``cols`` of ``df`` using the fitting
Parameters
----------
df : DataFrame
DataFrame to be preprocessed
"""
if not self._is_fitted:
raise NotFittedError("Fitting was not preformed")
pdu._is_cols_subset_of_df_cols(self.cols, df)
df = df.copy()
label_enc_dict = {}
for col in self.cols:
label_enc_dict[col] = self.les[col].transform(df[col])
labelenc_cols = pd.DataFrame(label_enc_dict,
# The index of the resulting DataFrame should be assigned and
# equal to the one of the original DataFrame. Otherwise, upon
# concatenation NaNs will be introduced.
index=df.index
)
for col in self.cols:
df[col] = labelenc_cols[col]
return df
def fit(self, df, y=None, **fit_params):
"""
Fitting the preprocessing
Parameters
----------
df : DataFrame
Data to use for fitting.
In many cases, should be ``X_train``.
"""
pdu._is_cols_subset_of_df_cols(self.cols, df)
for col in self.cols:
self.les[col].fit(df[col])
self._is_fitted = True
return self
这个类适合编码器的训练集,并在转换时使用适合的版本。代码的初始版本可以在这里找到。