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[WIP] FrequencyEncoder #11805

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[WIP] FrequencyEncoder #11805

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a713dc4
add Frequency Encoder
Aug 13, 2018
b2c9508
Fix docstring
Aug 13, 2018
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34 changes: 34 additions & 0 deletions sklearn/preprocessing/label.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
# Hamzeh Alsalhi <ha258@cornell.edu>
# License: BSD 3 clause

from collections import Counter
from collections import defaultdict
import itertools
import array
Expand Down Expand Up @@ -283,6 +284,39 @@ def inverse_transform(self, y):
return self.classes_[y]


class FrequencyEncoder(BaseEstimator, TransformerMixin):
"""If a value appears n times in data sent to fit, it is encoded as n."""

def fit(self, y):
"""Fit frequency encoder

Parameters
----------
y : array-like of shape (n_samples,)
Target values.

Returns
-------
self : returns an instance of self.
"""
y = column_or_1d(y, warn=True)
self._counts = Counter(y)
return self

def transform(self, y):
"""Transform labels to frequency encoding.
Parameters
----------
y : array-like of shape [n_samples]
Target values.

Returns
-------
y : array-like of shape [n_samples]
"""
return np.array([self._counts[v] for v in y])


class LabelBinarizer(BaseEstimator, TransformerMixin):
"""Binarize labels in a one-vs-all fashion

Expand Down