851 lines
33 KiB
Python
851 lines
33 KiB
Python
# Authors: Andreas Mueller <amueller@ais.uni-bonn.de>
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# Joris Van den Bossche <jorisvandenbossche@gmail.com>
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# License: BSD 3 clause
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from __future__ import division
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import numbers
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import warnings
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import numpy as np
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from scipy import sparse
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from .. import get_config as _get_config
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from ..base import BaseEstimator, TransformerMixin
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from ..utils import check_array
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from ..utils import deprecated
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from ..utils.fixes import _argmax, _object_dtype_isnan
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from ..utils.validation import check_is_fitted
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from .base import _transform_selected
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from .label import _encode, _encode_check_unknown
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__all__ = [
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'OneHotEncoder',
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'OrdinalEncoder'
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]
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class _BaseEncoder(BaseEstimator, TransformerMixin):
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"""
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Base class for encoders that includes the code to categorize and
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transform the input features.
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"""
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def _check_X(self, X):
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"""
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Perform custom check_array:
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- convert list of strings to object dtype
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- check for missing values for object dtype data (check_array does
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not do that)
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"""
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X_temp = check_array(X, dtype=None)
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if not hasattr(X, 'dtype') and np.issubdtype(X_temp.dtype, np.str_):
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X = check_array(X, dtype=np.object)
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else:
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X = X_temp
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if X.dtype == np.dtype('object'):
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if not _get_config()['assume_finite']:
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if _object_dtype_isnan(X).any():
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raise ValueError("Input contains NaN")
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return X
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def _fit(self, X, handle_unknown='error'):
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X = self._check_X(X)
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n_samples, n_features = X.shape
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if self._categories != 'auto':
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if X.dtype != object:
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for cats in self._categories:
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if not np.all(np.sort(cats) == np.array(cats)):
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raise ValueError("Unsorted categories are not "
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"supported for numerical categories")
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if len(self._categories) != n_features:
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raise ValueError("Shape mismatch: if n_values is an array,"
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" it has to be of shape (n_features,).")
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self.categories_ = []
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for i in range(n_features):
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Xi = X[:, i]
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if self._categories == 'auto':
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cats = _encode(Xi)
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else:
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cats = np.array(self._categories[i], dtype=X.dtype)
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if handle_unknown == 'error':
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diff = _encode_check_unknown(Xi, cats)
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if diff:
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msg = ("Found unknown categories {0} in column {1}"
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" during fit".format(diff, i))
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raise ValueError(msg)
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self.categories_.append(cats)
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def _transform(self, X, handle_unknown='error'):
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X = self._check_X(X)
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_, n_features = X.shape
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X_int = np.zeros_like(X, dtype=np.int)
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X_mask = np.ones_like(X, dtype=np.bool)
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for i in range(n_features):
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Xi = X[:, i]
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diff, valid_mask = _encode_check_unknown(Xi, self.categories_[i],
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return_mask=True)
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if not np.all(valid_mask):
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if handle_unknown == 'error':
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msg = ("Found unknown categories {0} in column {1}"
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" during transform".format(diff, i))
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raise ValueError(msg)
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else:
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# Set the problematic rows to an acceptable value and
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# continue `The rows are marked `X_mask` and will be
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# removed later.
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X_mask[:, i] = valid_mask
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# cast Xi into the largest string type necessary
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# to handle different lengths of numpy strings
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if (self.categories_[i].dtype.kind in ('U', 'S')
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and self.categories_[i].itemsize > Xi.itemsize):
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Xi = Xi.astype(self.categories_[i].dtype)
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else:
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Xi = Xi.copy()
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Xi[~valid_mask] = self.categories_[i][0]
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_, encoded = _encode(Xi, self.categories_[i], encode=True)
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X_int[:, i] = encoded
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return X_int, X_mask
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class OneHotEncoder(_BaseEncoder):
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"""Encode categorical integer features as a one-hot numeric array.
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The input to this transformer should be an array-like of integers or
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strings, denoting the values taken on by categorical (discrete) features.
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The features are encoded using a one-hot (aka 'one-of-K' or 'dummy')
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encoding scheme. This creates a binary column for each category and
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returns a sparse matrix or dense array.
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By default, the encoder derives the categories based on the unique values
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in each feature. Alternatively, you can also specify the `categories`
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manually.
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The OneHotEncoder previously assumed that the input features take on
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values in the range [0, max(values)). This behaviour is deprecated.
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This encoding is needed for feeding categorical data to many scikit-learn
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estimators, notably linear models and SVMs with the standard kernels.
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Note: a one-hot encoding of y labels should use a LabelBinarizer
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instead.
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Read more in the :ref:`User Guide <preprocessing_categorical_features>`.
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Parameters
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----------
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categories : 'auto' or a list of lists/arrays of values, default='auto'.
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Categories (unique values) per feature:
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- 'auto' : Determine categories automatically from the training data.
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- list : ``categories[i]`` holds the categories expected in the ith
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column. The passed categories should not mix strings and numeric
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values within a single feature, and should be sorted in case of
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numeric values.
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The used categories can be found in the ``categories_`` attribute.
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sparse : boolean, default=True
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Will return sparse matrix if set True else will return an array.
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dtype : number type, default=np.float
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Desired dtype of output.
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handle_unknown : 'error' or 'ignore', default='error'.
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Whether to raise an error or ignore if an unknown categorical feature
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is present during transform (default is to raise). When this parameter
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is set to 'ignore' and an unknown category is encountered during
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transform, the resulting one-hot encoded columns for this feature
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will be all zeros. In the inverse transform, an unknown category
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will be denoted as None.
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n_values : 'auto', int or array of ints, default='auto'
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Number of values per feature.
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- 'auto' : determine value range from training data.
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- int : number of categorical values per feature.
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Each feature value should be in ``range(n_values)``
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- array : ``n_values[i]`` is the number of categorical values in
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``X[:, i]``. Each feature value should be
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in ``range(n_values[i])``
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.. deprecated:: 0.20
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The `n_values` keyword was deprecated in version 0.20 and will
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be removed in 0.22. Use `categories` instead.
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categorical_features : 'all' or array of indices or mask, default='all'
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Specify what features are treated as categorical.
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- 'all': All features are treated as categorical.
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- array of indices: Array of categorical feature indices.
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- mask: Array of length n_features and with dtype=bool.
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Non-categorical features are always stacked to the right of the matrix.
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.. deprecated:: 0.20
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The `categorical_features` keyword was deprecated in version
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0.20 and will be removed in 0.22.
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You can use the ``ColumnTransformer`` instead.
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Attributes
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----------
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categories_ : list of arrays
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The categories of each feature determined during fitting
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(in order of the features in X and corresponding with the output
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of ``transform``).
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active_features_ : array
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Indices for active features, meaning values that actually occur
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in the training set. Only available when n_values is ``'auto'``.
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.. deprecated:: 0.20
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The ``active_features_`` attribute was deprecated in version
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0.20 and will be removed in 0.22.
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feature_indices_ : array of shape (n_features,)
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Indices to feature ranges.
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Feature ``i`` in the original data is mapped to features
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from ``feature_indices_[i]`` to ``feature_indices_[i+1]``
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(and then potentially masked by ``active_features_`` afterwards)
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.. deprecated:: 0.20
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The ``feature_indices_`` attribute was deprecated in version
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0.20 and will be removed in 0.22.
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n_values_ : array of shape (n_features,)
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Maximum number of values per feature.
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.. deprecated:: 0.20
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The ``n_values_`` attribute was deprecated in version
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0.20 and will be removed in 0.22.
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Examples
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--------
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Given a dataset with two features, we let the encoder find the unique
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values per feature and transform the data to a binary one-hot encoding.
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>>> from sklearn.preprocessing import OneHotEncoder
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>>> enc = OneHotEncoder(handle_unknown='ignore')
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>>> X = [['Male', 1], ['Female', 3], ['Female', 2]]
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>>> enc.fit(X)
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... # doctest: +ELLIPSIS
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... # doctest: +NORMALIZE_WHITESPACE
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OneHotEncoder(categorical_features=None, categories=None,
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dtype=<... 'numpy.float64'>, handle_unknown='ignore',
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n_values=None, sparse=True)
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>>> enc.categories_
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[array(['Female', 'Male'], dtype=object), array([1, 2, 3], dtype=object)]
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>>> enc.transform([['Female', 1], ['Male', 4]]).toarray()
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array([[1., 0., 1., 0., 0.],
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[0., 1., 0., 0., 0.]])
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>>> enc.inverse_transform([[0, 1, 1, 0, 0], [0, 0, 0, 1, 0]])
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array([['Male', 1],
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[None, 2]], dtype=object)
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>>> enc.get_feature_names()
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array(['x0_Female', 'x0_Male', 'x1_1', 'x1_2', 'x1_3'], dtype=object)
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See also
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--------
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sklearn.preprocessing.OrdinalEncoder : performs an ordinal (integer)
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encoding of the categorical features.
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sklearn.feature_extraction.DictVectorizer : performs a one-hot encoding of
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dictionary items (also handles string-valued features).
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sklearn.feature_extraction.FeatureHasher : performs an approximate one-hot
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encoding of dictionary items or strings.
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sklearn.preprocessing.LabelBinarizer : binarizes labels in a one-vs-all
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fashion.
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sklearn.preprocessing.MultiLabelBinarizer : transforms between iterable of
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iterables and a multilabel format, e.g. a (samples x classes) binary
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matrix indicating the presence of a class label.
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"""
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def __init__(self, n_values=None, categorical_features=None,
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categories=None, sparse=True, dtype=np.float64,
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handle_unknown='error'):
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self.categories = categories
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self.sparse = sparse
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self.dtype = dtype
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self.handle_unknown = handle_unknown
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self.n_values = n_values
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self.categorical_features = categorical_features
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# Deprecated attributes
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@property
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@deprecated("The ``active_features_`` attribute was deprecated in version "
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"0.20 and will be removed 0.22.")
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def active_features_(self):
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check_is_fitted(self, 'categories_')
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return self._active_features_
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@property
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@deprecated("The ``feature_indices_`` attribute was deprecated in version "
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"0.20 and will be removed 0.22.")
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def feature_indices_(self):
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check_is_fitted(self, 'categories_')
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return self._feature_indices_
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@property
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@deprecated("The ``n_values_`` attribute was deprecated in version "
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"0.20 and will be removed 0.22.")
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def n_values_(self):
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check_is_fitted(self, 'categories_')
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return self._n_values_
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def _handle_deprecations(self, X):
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# internal version of the attributes to handle deprecations
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self._n_values = self.n_values
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self._categories = getattr(self, '_categories', None)
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self._categorical_features = getattr(self, '_categorical_features',
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None)
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# user manually set the categories or second fit -> never legacy mode
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if self.categories is not None or self._categories is not None:
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self._legacy_mode = False
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if self.categories is not None:
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self._categories = self.categories
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# categories not set -> infer if we need legacy mode or not
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elif self.n_values is not None and self.n_values != 'auto':
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msg = (
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"Passing 'n_values' is deprecated in version 0.20 and will be "
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"removed in 0.22. You can use the 'categories' keyword "
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"instead. 'n_values=n' corresponds to 'categories=[range(n)]'."
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)
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warnings.warn(msg, DeprecationWarning)
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self._legacy_mode = True
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else: # n_values = 'auto'
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# n_values can also be None (default to catch usage), so set
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# _n_values to 'auto' explicitly
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self._n_values = 'auto'
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if self.handle_unknown == 'ignore':
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# no change in behaviour, no need to raise deprecation warning
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self._legacy_mode = False
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self._categories = 'auto'
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if self.n_values == 'auto':
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# user manually specified this
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msg = (
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"Passing 'n_values' is deprecated in version 0.20 and "
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"will be removed in 0.22. n_values='auto' can be "
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"replaced with categories='auto'."
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)
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warnings.warn(msg, DeprecationWarning)
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else:
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# check if we have integer or categorical input
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try:
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check_array(X, dtype=np.int)
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except ValueError:
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self._legacy_mode = False
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self._categories = 'auto'
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else:
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msg = (
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"The handling of integer data will change in version "
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"0.22. Currently, the categories are determined "
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"based on the range [0, max(values)], while in the "
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"future they will be determined based on the unique "
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"values.\nIf you want the future behaviour and "
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"silence this warning, you can specify "
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"\"categories='auto'\".\n"
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"In case you used a LabelEncoder before this "
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"OneHotEncoder to convert the categories to integers, "
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"then you can now use the OneHotEncoder directly."
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)
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warnings.warn(msg, FutureWarning)
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self._legacy_mode = True
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# if user specified categorical_features -> always use legacy mode
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if self.categorical_features is not None:
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if (isinstance(self.categorical_features, str)
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and self.categorical_features == 'all'):
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warnings.warn(
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"The 'categorical_features' keyword is deprecated in "
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"version 0.20 and will be removed in 0.22. The passed "
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"value of 'all' is the default and can simply be removed.",
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DeprecationWarning)
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else:
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if self.categories is not None:
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raise ValueError(
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"The 'categorical_features' keyword is deprecated, "
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"and cannot be used together with specifying "
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"'categories'.")
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warnings.warn(
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"The 'categorical_features' keyword is deprecated in "
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"version 0.20 and will be removed in 0.22. You can "
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"use the ColumnTransformer instead.", DeprecationWarning)
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# Set categories_ to empty list if no categorical columns exist
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n_features = X.shape[1]
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sel = np.zeros(n_features, dtype=bool)
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sel[np.asarray(self.categorical_features)] = True
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if sum(sel) == 0:
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self.categories_ = []
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self._legacy_mode = True
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self._categorical_features = self.categorical_features
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else:
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self._categorical_features = 'all'
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def fit(self, X, y=None):
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"""Fit OneHotEncoder to X.
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Parameters
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----------
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X : array-like, shape [n_samples, n_features]
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The data to determine the categories of each feature.
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Returns
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-------
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self
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"""
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if self.handle_unknown not in ('error', 'ignore'):
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msg = ("handle_unknown should be either 'error' or 'ignore', "
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"got {0}.".format(self.handle_unknown))
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raise ValueError(msg)
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self._handle_deprecations(X)
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if self._legacy_mode:
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_transform_selected(X, self._legacy_fit_transform, self.dtype,
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self._categorical_features,
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copy=True)
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return self
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else:
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self._fit(X, handle_unknown=self.handle_unknown)
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return self
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def _legacy_fit_transform(self, X):
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"""Assumes X contains only categorical features."""
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dtype = getattr(X, 'dtype', None)
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X = check_array(X, dtype=np.int)
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if np.any(X < 0):
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raise ValueError("OneHotEncoder in legacy mode cannot handle "
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"categories encoded as negative integers. "
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"Please set categories='auto' explicitly to "
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"be able to use arbitrary integer values as "
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"category identifiers.")
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n_samples, n_features = X.shape
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if (isinstance(self._n_values, str) and
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self._n_values == 'auto'):
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n_values = np.max(X, axis=0) + 1
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elif isinstance(self._n_values, numbers.Integral):
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if (np.max(X, axis=0) >= self._n_values).any():
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raise ValueError("Feature out of bounds for n_values=%d"
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% self._n_values)
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n_values = np.empty(n_features, dtype=np.int)
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n_values.fill(self._n_values)
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else:
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try:
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n_values = np.asarray(self._n_values, dtype=int)
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except (ValueError, TypeError):
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raise TypeError("Wrong type for parameter `n_values`. Expected"
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" 'auto', int or array of ints, got %r"
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% type(self._n_values))
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if n_values.ndim < 1 or n_values.shape[0] != X.shape[1]:
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raise ValueError("Shape mismatch: if n_values is an array,"
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" it has to be of shape (n_features,).")
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self._n_values_ = n_values
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self.categories_ = [np.arange(n_val - 1, dtype=dtype)
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for n_val in n_values]
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n_values = np.hstack([[0], n_values])
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indices = np.cumsum(n_values)
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self._feature_indices_ = indices
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column_indices = (X + indices[:-1]).ravel()
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row_indices = np.repeat(np.arange(n_samples, dtype=np.int32),
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n_features)
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data = np.ones(n_samples * n_features)
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out = sparse.coo_matrix((data, (row_indices, column_indices)),
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shape=(n_samples, indices[-1]),
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dtype=self.dtype).tocsr()
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if (isinstance(self._n_values, str) and
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self._n_values == 'auto'):
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mask = np.array(out.sum(axis=0)).ravel() != 0
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active_features = np.where(mask)[0]
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out = out[:, active_features]
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self._active_features_ = active_features
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self.categories_ = [
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np.unique(X[:, i]).astype(dtype) if dtype
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else np.unique(X[:, i]) for i in range(n_features)]
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return out if self.sparse else out.toarray()
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def fit_transform(self, X, y=None):
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"""Fit OneHotEncoder to X, then transform X.
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Equivalent to fit(X).transform(X) but more convenient.
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Parameters
|
|
----------
|
|
X : array-like, shape [n_samples, n_features]
|
|
The data to encode.
|
|
|
|
Returns
|
|
-------
|
|
X_out : sparse matrix if sparse=True else a 2-d array
|
|
Transformed input.
|
|
"""
|
|
if self.handle_unknown not in ('error', 'ignore'):
|
|
msg = ("handle_unknown should be either 'error' or 'ignore', "
|
|
"got {0}.".format(self.handle_unknown))
|
|
raise ValueError(msg)
|
|
|
|
self._handle_deprecations(X)
|
|
|
|
if self._legacy_mode:
|
|
return _transform_selected(
|
|
X, self._legacy_fit_transform, self.dtype,
|
|
self._categorical_features, copy=True)
|
|
else:
|
|
return self.fit(X).transform(X)
|
|
|
|
def _legacy_transform(self, X):
|
|
"""Assumes X contains only categorical features."""
|
|
X = check_array(X, dtype=np.int)
|
|
if np.any(X < 0):
|
|
raise ValueError("OneHotEncoder in legacy mode cannot handle "
|
|
"categories encoded as negative integers. "
|
|
"Please set categories='auto' explicitly to "
|
|
"be able to use arbitrary integer values as "
|
|
"category identifiers.")
|
|
n_samples, n_features = X.shape
|
|
|
|
indices = self._feature_indices_
|
|
if n_features != indices.shape[0] - 1:
|
|
raise ValueError("X has different shape than during fitting."
|
|
" Expected %d, got %d."
|
|
% (indices.shape[0] - 1, n_features))
|
|
|
|
# We use only those categorical features of X that are known using fit.
|
|
# i.e lesser than n_values_ using mask.
|
|
# This means, if self.handle_unknown is "ignore", the row_indices and
|
|
# col_indices corresponding to the unknown categorical feature are
|
|
# ignored.
|
|
mask = (X < self._n_values_).ravel()
|
|
if np.any(~mask):
|
|
if self.handle_unknown not in ['error', 'ignore']:
|
|
raise ValueError("handle_unknown should be either error or "
|
|
"unknown got %s" % self.handle_unknown)
|
|
if self.handle_unknown == 'error':
|
|
raise ValueError("unknown categorical feature present %s "
|
|
"during transform." % X.ravel()[~mask])
|
|
|
|
column_indices = (X + indices[:-1]).ravel()[mask]
|
|
row_indices = np.repeat(np.arange(n_samples, dtype=np.int32),
|
|
n_features)[mask]
|
|
data = np.ones(np.sum(mask))
|
|
out = sparse.coo_matrix((data, (row_indices, column_indices)),
|
|
shape=(n_samples, indices[-1]),
|
|
dtype=self.dtype).tocsr()
|
|
if (isinstance(self._n_values, str) and
|
|
self._n_values == 'auto'):
|
|
out = out[:, self._active_features_]
|
|
|
|
return out if self.sparse else out.toarray()
|
|
|
|
def _transform_new(self, X):
|
|
"""New implementation assuming categorical input"""
|
|
X_temp = check_array(X, dtype=None)
|
|
if not hasattr(X, 'dtype') and np.issubdtype(X_temp.dtype, np.str_):
|
|
X = check_array(X, dtype=np.object)
|
|
else:
|
|
X = X_temp
|
|
|
|
n_samples, n_features = X.shape
|
|
|
|
X_int, X_mask = self._transform(X, handle_unknown=self.handle_unknown)
|
|
|
|
mask = X_mask.ravel()
|
|
n_values = [cats.shape[0] for cats in self.categories_]
|
|
n_values = np.array([0] + n_values)
|
|
feature_indices = np.cumsum(n_values)
|
|
|
|
indices = (X_int + feature_indices[:-1]).ravel()[mask]
|
|
indptr = X_mask.sum(axis=1).cumsum()
|
|
indptr = np.insert(indptr, 0, 0)
|
|
data = np.ones(n_samples * n_features)[mask]
|
|
|
|
out = sparse.csr_matrix((data, indices, indptr),
|
|
shape=(n_samples, feature_indices[-1]),
|
|
dtype=self.dtype)
|
|
if not self.sparse:
|
|
return out.toarray()
|
|
else:
|
|
return out
|
|
|
|
def transform(self, X):
|
|
"""Transform X using one-hot encoding.
|
|
|
|
Parameters
|
|
----------
|
|
X : array-like, shape [n_samples, n_features]
|
|
The data to encode.
|
|
|
|
Returns
|
|
-------
|
|
X_out : sparse matrix if sparse=True else a 2-d array
|
|
Transformed input.
|
|
"""
|
|
check_is_fitted(self, 'categories_')
|
|
if self._legacy_mode:
|
|
return _transform_selected(X, self._legacy_transform, self.dtype,
|
|
self._categorical_features,
|
|
copy=True)
|
|
else:
|
|
return self._transform_new(X)
|
|
|
|
def inverse_transform(self, X):
|
|
"""Convert the back data to the original representation.
|
|
|
|
In case unknown categories are encountered (all zero's in the
|
|
one-hot encoding), ``None`` is used to represent this category.
|
|
|
|
Parameters
|
|
----------
|
|
X : array-like or sparse matrix, shape [n_samples, n_encoded_features]
|
|
The transformed data.
|
|
|
|
Returns
|
|
-------
|
|
X_tr : array-like, shape [n_samples, n_features]
|
|
Inverse transformed array.
|
|
|
|
"""
|
|
# if self._legacy_mode:
|
|
# raise ValueError("only supported for categorical features")
|
|
|
|
check_is_fitted(self, 'categories_')
|
|
X = check_array(X, accept_sparse='csr')
|
|
|
|
n_samples, _ = X.shape
|
|
n_features = len(self.categories_)
|
|
n_transformed_features = sum([len(cats) for cats in self.categories_])
|
|
|
|
# validate shape of passed X
|
|
msg = ("Shape of the passed X data is not correct. Expected {0} "
|
|
"columns, got {1}.")
|
|
if X.shape[1] != n_transformed_features:
|
|
raise ValueError(msg.format(n_transformed_features, X.shape[1]))
|
|
|
|
# create resulting array of appropriate dtype
|
|
dt = np.find_common_type([cat.dtype for cat in self.categories_], [])
|
|
X_tr = np.empty((n_samples, n_features), dtype=dt)
|
|
|
|
j = 0
|
|
found_unknown = {}
|
|
|
|
for i in range(n_features):
|
|
n_categories = len(self.categories_[i])
|
|
sub = X[:, j:j + n_categories]
|
|
|
|
# for sparse X argmax returns 2D matrix, ensure 1D array
|
|
labels = np.asarray(_argmax(sub, axis=1)).flatten()
|
|
X_tr[:, i] = self.categories_[i][labels]
|
|
|
|
if self.handle_unknown == 'ignore':
|
|
# ignored unknown categories: we have a row of all zero's
|
|
unknown = np.asarray(sub.sum(axis=1) == 0).flatten()
|
|
if unknown.any():
|
|
found_unknown[i] = unknown
|
|
|
|
j += n_categories
|
|
|
|
# if ignored are found: potentially need to upcast result to
|
|
# insert None values
|
|
if found_unknown:
|
|
if X_tr.dtype != object:
|
|
X_tr = X_tr.astype(object)
|
|
|
|
for idx, mask in found_unknown.items():
|
|
X_tr[mask, idx] = None
|
|
|
|
return X_tr
|
|
|
|
def get_feature_names(self, input_features=None):
|
|
"""Return feature names for output features.
|
|
|
|
Parameters
|
|
----------
|
|
input_features : list of string, length n_features, optional
|
|
String names for input features if available. By default,
|
|
"x0", "x1", ... "xn_features" is used.
|
|
|
|
Returns
|
|
-------
|
|
output_feature_names : array of string, length n_output_features
|
|
|
|
"""
|
|
check_is_fitted(self, 'categories_')
|
|
cats = self.categories_
|
|
if input_features is None:
|
|
input_features = ['x%d' % i for i in range(len(cats))]
|
|
elif len(input_features) != len(self.categories_):
|
|
raise ValueError(
|
|
"input_features should have length equal to number of "
|
|
"features ({}), got {}".format(len(self.categories_),
|
|
len(input_features)))
|
|
|
|
feature_names = []
|
|
for i in range(len(cats)):
|
|
names = [
|
|
input_features[i] + '_' + str(t) for t in cats[i]]
|
|
feature_names.extend(names)
|
|
|
|
return np.array(feature_names, dtype=object)
|
|
|
|
|
|
class OrdinalEncoder(_BaseEncoder):
|
|
"""Encode categorical features as an integer array.
|
|
|
|
The input to this transformer should be an array-like of integers or
|
|
strings, denoting the values taken on by categorical (discrete) features.
|
|
The features are converted to ordinal integers. This results in
|
|
a single column of integers (0 to n_categories - 1) per feature.
|
|
|
|
Read more in the :ref:`User Guide <preprocessing_categorical_features>`.
|
|
|
|
Parameters
|
|
----------
|
|
categories : 'auto' or a list of lists/arrays of values.
|
|
Categories (unique values) per feature:
|
|
|
|
- 'auto' : Determine categories automatically from the training data.
|
|
- list : ``categories[i]`` holds the categories expected in the ith
|
|
column. The passed categories should not mix strings and numeric
|
|
values, and should be sorted in case of numeric values.
|
|
|
|
The used categories can be found in the ``categories_`` attribute.
|
|
|
|
dtype : number type, default np.float64
|
|
Desired dtype of output.
|
|
|
|
Attributes
|
|
----------
|
|
categories_ : list of arrays
|
|
The categories of each feature determined during fitting
|
|
(in order of the features in X and corresponding with the output
|
|
of ``transform``).
|
|
|
|
Examples
|
|
--------
|
|
Given a dataset with two features, we let the encoder find the unique
|
|
values per feature and transform the data to an ordinal encoding.
|
|
|
|
>>> from sklearn.preprocessing import OrdinalEncoder
|
|
>>> enc = OrdinalEncoder()
|
|
>>> X = [['Male', 1], ['Female', 3], ['Female', 2]]
|
|
>>> enc.fit(X)
|
|
... # doctest: +ELLIPSIS
|
|
OrdinalEncoder(categories='auto', dtype=<... 'numpy.float64'>)
|
|
>>> enc.categories_
|
|
[array(['Female', 'Male'], dtype=object), array([1, 2, 3], dtype=object)]
|
|
>>> enc.transform([['Female', 3], ['Male', 1]])
|
|
array([[0., 2.],
|
|
[1., 0.]])
|
|
|
|
>>> enc.inverse_transform([[1, 0], [0, 1]])
|
|
array([['Male', 1],
|
|
['Female', 2]], dtype=object)
|
|
|
|
See also
|
|
--------
|
|
sklearn.preprocessing.OneHotEncoder : performs a one-hot encoding of
|
|
categorical features.
|
|
sklearn.preprocessing.LabelEncoder : encodes target labels with values
|
|
between 0 and n_classes-1.
|
|
"""
|
|
|
|
def __init__(self, categories='auto', dtype=np.float64):
|
|
self.categories = categories
|
|
self.dtype = dtype
|
|
|
|
def fit(self, X, y=None):
|
|
"""Fit the OrdinalEncoder to X.
|
|
|
|
Parameters
|
|
----------
|
|
X : array-like, shape [n_samples, n_features]
|
|
The data to determine the categories of each feature.
|
|
|
|
Returns
|
|
-------
|
|
self
|
|
|
|
"""
|
|
# base classes uses _categories to deal with deprecations in
|
|
# OneHoteEncoder: can be removed once deprecations are removed
|
|
self._categories = self.categories
|
|
self._fit(X)
|
|
|
|
return self
|
|
|
|
def transform(self, X):
|
|
"""Transform X to ordinal codes.
|
|
|
|
Parameters
|
|
----------
|
|
X : array-like, shape [n_samples, n_features]
|
|
The data to encode.
|
|
|
|
Returns
|
|
-------
|
|
X_out : sparse matrix or a 2-d array
|
|
Transformed input.
|
|
|
|
"""
|
|
X_int, _ = self._transform(X)
|
|
return X_int.astype(self.dtype, copy=False)
|
|
|
|
def inverse_transform(self, X):
|
|
"""Convert the data back to the original representation.
|
|
|
|
Parameters
|
|
----------
|
|
X : array-like or sparse matrix, shape [n_samples, n_encoded_features]
|
|
The transformed data.
|
|
|
|
Returns
|
|
-------
|
|
X_tr : array-like, shape [n_samples, n_features]
|
|
Inverse transformed array.
|
|
|
|
"""
|
|
check_is_fitted(self, 'categories_')
|
|
X = check_array(X, accept_sparse='csr')
|
|
|
|
n_samples, _ = X.shape
|
|
n_features = len(self.categories_)
|
|
|
|
# validate shape of passed X
|
|
msg = ("Shape of the passed X data is not correct. Expected {0} "
|
|
"columns, got {1}.")
|
|
if X.shape[1] != n_features:
|
|
raise ValueError(msg.format(n_features, X.shape[1]))
|
|
|
|
# create resulting array of appropriate dtype
|
|
dt = np.find_common_type([cat.dtype for cat in self.categories_], [])
|
|
X_tr = np.empty((n_samples, n_features), dtype=dt)
|
|
|
|
for i in range(n_features):
|
|
labels = X[:, i].astype('int64')
|
|
X_tr[:, i] = self.categories_[i][labels]
|
|
|
|
return X_tr
|