Skip to content

Commit

Permalink
Unawareness refactor (#162)
Browse files Browse the repository at this point in the history
* Added strategy option to use mdi as measure

* Removed mdi strategy

* Added classes for both unawareness strategies

* Docstring cleanup

* Deleted old unawareness class

* Fixed correlation suppression
  • Loading branch information
reluzita authored Feb 8, 2024
1 parent af9742a commit 59c1a02
Show file tree
Hide file tree
Showing 2 changed files with 160 additions and 58 deletions.
Original file line number Diff line number Diff line change
@@ -1,51 +1,29 @@
from typing import Optional, Literal

from typing import Optional
import pandas as pd
import numpy as np
from scipy.stats import chi2_contingency

from ...utils import create_logger
from .preprocessing import PreProcessing


class Unawareness(PreProcessing):
def __init__(
self,
correlation_threshold: Optional[float] = 0.5,
strategy: Literal["correlation", "featureselection"] = "correlation",
seed: int = 0,
):
class CorrelaitonSuppression(PreProcessing):
def __init__(self, correlation_threshold: Optional[float] = 0.5):
"""Removes features that are highly correlated with the sensitive attribute.
Note: For this method, the vector s (protected attribute) is assumed to be
categorical.
Parameters
----------
top_k : int, optional
Number of features to remove. If None, the correlation_threshold
must be passed by the user. Defaults to 1.
correlation_threshold : float, optional
Features with a correlation value higher than this thresold are
removed. If None, the top_k parameter is used to determine how many
features to remove. Defaults to None.
strategy : {"correlation", "featureselection"}, optional
Strategy to use to calculate how much each feature is related to the
sensitive attribute. If "correlation", correlation between features
is used. "featureselection" is not implemented yet. Defaults to
"correlation".
"""
self.logger = create_logger("methods.preprocessing.Unawareness")
self.logger.info("Instantiating an Unawareness preprocessing method.")
self.logger = create_logger("methods.preprocessing.CorrelaitonSuppression")
self.logger.info(
"Instantiating an CorrelaitonSuppression preprocessing method."
)
self.used_in_inference = True

self.correlation_threshold = correlation_threshold
if strategy == "featureselection":
raise NotImplementedError(
"The feature selection strategy is not implemented yet."
)
self.strategy = strategy
self.seed = seed

def _correlation_ratio(
self, categorical_feature: np.ndarray, numeric_feature: np.ndarray
Expand All @@ -57,14 +35,12 @@ def _correlation_ratio(
the numeric data is purely due to the difference within the categorical
data. A value of 0 indicates that the variance in the numeric data is
completely unaffected by any differences within the categorical data.
Parameters
----------
categorical_feature : numpy.ndarray
Categorical column.
numeric_feature : numpy.ndarray
Numeric column.
Returns
-------
float
Expand All @@ -89,14 +65,12 @@ def _cramerv(self, a: np.ndarray, b: np.ndarray):
Cramer's V is a heavily biased estimator and tends to overestimate the
strength of the correlation. Therefore, a biased correction is normally
applied to the statistic.
Parameters
----------
a : numpy.ndarray
First categorical column.
b : numpy.ndarray
Second categorical column.
Returns
-------
float
Expand All @@ -107,16 +81,14 @@ def _cramerv(self, a: np.ndarray, b: np.ndarray):
n = np.sum(contingency.values)
r, k = contingency.shape
phi2 = chi2 / n

phi2_corrected = max(0, phi2 - (k - 1) * (r - 1) / (n - 1))
r_corrected = r - (r - 1) ** 2 / (n - 1)
k_corrected = k - (k - 1) ** 2 / (n - 1)

statistic = np.sqrt(phi2_corrected / min(r_corrected - 1, k_corrected - 1))
return statistic

def fit(self, X: pd.DataFrame, y: pd.Series, s: Optional[pd.Series]) -> None:
"""Calculates how related each feature is to the sensitive attribute.
"""Calculates correlation between each feature and the sensitive attribute.
Parameters
----------
Expand All @@ -128,24 +100,24 @@ def fit(self, X: pd.DataFrame, y: pd.Series, s: Optional[pd.Series]) -> None:
Protected attribute vector.
"""
super().fit(X, y, s)

self.logger.info("Calculating feature correlation with sensitive attribute.")

if self.strategy == "correlation":
self.scores = pd.Series(index=X.columns)
for col in X.columns:
if X[col].dtype.name == "category":
self.scores[col] = self._cramerv(s.values, X[col].values)
else:
self.scores[col] = self._correlation_ratio(s.values, X[col].values)

self.scores = self.scores.sort_values(ascending=False)
self.logger.info(
"Identifying features correlated with the sensitive attribute."
)
scores = pd.Series(index=X.columns)
for col in X.columns:
if X[col].dtype.name == "category":
scores[col] = self._cramerv(s.values, X[col].values)
else:
scores[col] = self._correlation_ratio(s.values, X[col].values)
scores = scores.sort_values(ascending=False)
self.remove_features = list(
scores.loc[scores >= self.correlation_threshold].index
)

def transform(
self, X: pd.DataFrame, y: pd.Series, s: Optional[pd.Series] = None
) -> tuple[pd.DataFrame, pd.Series, pd.Series]:
"""Removes the most correlated features with the sensitive attribute.
Parameters
----------
X : pd.DataFrame
Expand All @@ -154,22 +126,15 @@ def transform(
Label vector.
s : pd.Series, optional
Protected attribute vector.
Returns
-------
tuple[pd.DataFrame, pd.Series, pd.Series]
The transformed input, X, y, and s.
"""
super().transform(X, y, s)

remove_features = list(
self.scores.loc[self.scores >= self.correlation_threshold].index
)

self.logger.info(
f"Removing most correlated features with sensitive attribute: "
f"{remove_features}"
f"{self.remove_features}"
)
X_transformed = X.drop(columns=remove_features)

X_transformed = X.drop(columns=self.remove_features)
return X_transformed, y, s
Original file line number Diff line number Diff line change
@@ -0,0 +1,137 @@
from typing import Optional

import pandas as pd
from sklearn.ensemble import RandomForestClassifier
from sklearn.model_selection import train_test_split
from sklearn.metrics import roc_auc_score

from ...utils import create_logger
from .preprocessing import PreProcessing


class FeatureImportanceSuppression(PreProcessing):
def __init__(
self,
auc_threshold: Optional[int] = 0.5,
feature_importance_threshold: Optional[float] = 0.1,
n_estimators: Optional[int] = 10,
seed: int = 0,
):
"""Iterively removes the most important features with respect to the sensitive
attribute.
Parameters
----------
auc_threshold : int, optional
The value of AUC above which the removal of features continues. Defaults to
0.5.
feature_importance_threshold : float, optional
The value of feature importance above which the most important feature needs
to have to be removed. Defaults to 0.1.
n_estimators : int, optional
The number of trees in the random forest. Defaults to 10.
seed : int, optional
The seed for the random forest. Defaults to 0.
"""
self.logger = create_logger(
"methods.preprocessing.FeatureImportanceSuppression"
)
self.logger.info(
"Instantiating a FeatureImportanceSuppression preprocessing method."
)
self.used_in_inference = True

self.auc_threshold = auc_threshold
self.feature_importance_threshold = feature_importance_threshold
self.n_estimators = n_estimators
self.seed = seed

def fit(self, X: pd.DataFrame, y: pd.Series, s: Optional[pd.Series]) -> None:
"""Iteratively removes the most important features to predict the sensitive
attribute.
Parameters
----------
X : pandas.DataFrame
Feature matrix.
y : pandas.Series
Label vector.
s : pandas.Series
Protected attribute vector.
"""
super().fit(X, y, s)

self.logger.info("Identifying features to remove.")

rf = RandomForestClassifier(
n_estimators=self.n_estimators, random_state=self.seed
)

features = pd.concat([X, y], axis=1)
features = pd.get_dummies(features)
target = s.copy()

features_train, features_val, target_train, target_val = train_test_split(
features, target
)
self.remove_features = []

while features_train.shape[1] > 1:
rf.fit(features_train, target_train)
predictions = rf.predict_proba(features_val)[:, 1]
auc = roc_auc_score(target_val, predictions)

if auc > self.auc_threshold:
scores = pd.Series(
rf.feature_importances_, index=features_train.columns
)
feature = scores.sort_values(ascending=False).index[0]
if scores[feature] < self.feature_importance_threshold:
break

i = feature.rfind("_")
if feature[:i] in X.columns:
eliminate = [
col
for col in features_train.columns
if col.startswith(feature[:i])
]
self.remove_features.append(feature[:i])
else:
eliminate = [feature]
self.remove_features.append(feature)

features_train = features_train.drop(columns=eliminate)
features_val = features_val.drop(columns=eliminate)
else:
break

def transform(
self, X: pd.DataFrame, y: pd.Series, s: Optional[pd.Series] = None
) -> tuple[pd.DataFrame, pd.Series, pd.Series]:
"""Removes the features which are related with the sensitive attribute the most
from the data.
Parameters
----------
X : pd.DataFrame
Feature matrix.
y : pd.Series
Label vector.
s : pd.Series, optional
Protected attribute vector.
Returns
-------
tuple[pd.DataFrame, pd.Series, pd.Series]
The transformed input, X, y, and s.
"""
super().transform(X, y, s)

self.logger.info(
f"Removing most correlated features with sensitive attribute: "
f"{self.remove_features}"
)
X_transformed = X.drop(columns=self.remove_features)

return X_transformed, y, s

0 comments on commit 59c1a02

Please sign in to comment.