""" This module implements all classes needed to perform data minimization """ from typing import Union import pandas as pd import numpy as np import copy import sys from scipy.spatial import distance from sklearn.base import BaseEstimator, TransformerMixin, MetaEstimatorMixin from sklearn.compose import ColumnTransformer from sklearn.impute import SimpleImputer from sklearn.pipeline import Pipeline from sklearn.preprocessing import OneHotEncoder from sklearn.utils.validation import check_X_y, check_array, check_is_fitted from sklearn.tree import DecisionTreeClassifier from sklearn.model_selection import train_test_split class GeneralizeToRepresentative(BaseEstimator, MetaEstimatorMixin, TransformerMixin): """ A transformer that generalizes data to representative points. Learns data generalizations based on an original model's predictions and a target accuracy. Once the generalizations are learned, can receive one or more data records and transform them to representative points based on the learned generalization. An alternative way to use the transformer is to supply ``cells`` and ``features`` in init or set_params and those will be used to transform data to representatives. In this case, fit must still be called but there is no need to supply it with ``X`` and ``y``, and there is no need to supply an existing ``estimator`` to init. In summary, either ``estimator`` and ``target_accuracy`` should be supplied or ``cells`` and ``features`` should be supplied. Parameters ---------- estimator : estimator, optional The original model for which generalization is being performed. Should be pre-fitted. target_accuracy : float, optional The required accuracy when applying the base model to the generalized data. Accuracy is measured relative to the original accuracy of the model. features : list of str, optional The feature names, in the order that they appear in the data. categorical_features: list of str, optional The list of categorical features should only be supplied when passing data as a pandas dataframe. features_to_minimize: List of str or numbers, optional The features that need to be minimized in case of pandas data, and indexes of features in case of numpy data. cells : list of object, optional The cells used to generalize records. Each cell must define a range or subset of categories for each feature, as well as a representative value for each feature. This parameter should be used when instantiating a transformer object without first fitting it. train_only_QI : Bool, optional The required method to train data set for minimizing. Default is to train the tree just on the features that are given as features_to_minimize. Attributes ---------- cells_ : list of object The cells used to generalize records, as learned when calling fit. ncp_ : float The NCP (information loss) score of the resulting generalization, as measured on the training data. generalizations_ : object The generalizations that were learned (actual feature ranges). Notes ----- """ def __init__(self, estimator=None, target_accuracy=0.998, features=None, cells=None, categorical_features=None, features_to_minimize: Union[np.ndarray, list] = None , train_only_QI=True): self.estimator = estimator self.target_accuracy = target_accuracy self.features = features self.cells = cells self.categorical_features = [] if categorical_features: self.categorical_features = categorical_features self.features_to_minimize = features_to_minimize self.train_only_QI = train_only_QI def get_params(self, deep=True): """Get parameters for this estimator. Parameters ---------- deep : boolean, optional If True, will return the parameters for this estimator and contained subobjects that are estimators. Returns ------- params : mapping of string to any Parameter names mapped to their values. """ ret = {} ret['target_accuracy'] = self.target_accuracy if deep: ret['features'] = copy.deepcopy(self.features) ret['cells'] = copy.deepcopy(self.cells) ret['estimator'] = self.estimator else: ret['features'] = copy.copy(self.features) ret['cells'] = copy.copy(self.cells) return ret def set_params(self, **params): """Set the parameters of this estimator. Returns ------- self : object Returns self. """ if 'target_accuracy' in params: self.target_accuracy = params['target_accuracy'] if 'features' in params: self.features = params['features'] if 'cells' in params: self.cells = params['cells'] return self @property def generalizations(self): return self.generalizations_ def fit_transform(self, X: Union[np.ndarray, pd.DataFrame] = None, y: Union[np.ndarray, pd.DataFrame] = None): """Learns the generalizations based on training data, and applies them to the data. Parameters ---------- X : {array-like, sparse matrix}, shape (n_samples, n_features), optional The training input samples. y : array-like, shape (n_samples,), optional The target values. An array of int. This should contain the predictions of the original model on ``X``. Returns ------- X_transformed : numpy or pandas according to the input type, shape (n_samples, n_features) The array containing the representative values to which each record in ``X`` is mapped. """ self.fit(X, y) return self.transform(X) def fit(self, X: Union[np.ndarray, pd.DataFrame] = None, y: Union[np.ndarray, pd.DataFrame] = None): """Learns the generalizations based on training data. Parameters ---------- X : {array-like, sparse matrix}, shape (n_samples, n_features), optional The training input samples. y : array-like, shape (n_samples,), optional The target values. An array of int. This should contain the predictions of the original model on ``X``. Returns ------- X_transformed : numpy or pandas according to the input type, shape (n_samples, n_features) The array containing the representative values to which each record in ``X`` is mapped. """ # take into account that estimator, X, y, cells, features may be None if X is not None: if type(X) == np.ndarray: self.is_numpy = True else: self.is_numpy = False if X is not None and y is not None: if self.is_numpy: X, y = check_X_y(X, y, accept_sparse=True) self.n_features_ = X.shape[1] elif self.features: self.n_features_ = len(self.features) else: self.n_features_ = 0 if self.features: self._features = self.features # if features is None, use numbers instead of names elif self.n_features_ != 0: self._features = [i for i in range(self.n_features_)] else: self._features = None if self.cells: self.cells_ = self.cells else: self.cells_ = {} self.categorical_values = {} # Going to fit # (currently not dealing with option to fit with only X and y and no estimator) if self.estimator and X is not None and y is not None: if self.is_numpy: if not self.features_to_minimize: self.features_to_minimize = [i for i in range(len(self._features))] x_QI = X[:, self.features_to_minimize] self.features_to_minimize = [self._features[i] for i in self.features_to_minimize] X = pd.DataFrame(X, columns=self._features) else: if not self.features_to_minimize: self.features_to_minimize = self._features x_QI = X.loc[:, self.features_to_minimize] x_QI = pd.DataFrame(x_QI, columns=self.features_to_minimize) # divide dataset into train and test used_data = X if self.train_only_QI: used_data = x_QI X_train, X_test, y_train, y_test = train_test_split(X, y, stratify=y, test_size=0.4, random_state=18) X_train_QI = X_train.loc[:, self.features_to_minimize] X_test_QI = X_test.loc[:, self.features_to_minimize] used_X_train = X_train if self.train_only_QI: used_X_train = X_train_QI # collect feature data (such as min, max) feature_data = {} for feature in self._features: if feature not in feature_data.keys(): fd = {} values = list(X.loc[:, feature]) if feature not in self.categorical_features: fd['min'] = min(values) fd['max'] = max(values) fd['range'] = max(values) - min(values) else: fd['range'] = len(values) feature_data[feature] = fd # prepare data for DT categorical_features = [f for f in self._features if f in self.categorical_features and f in self.features_to_minimize] numeric_transformer = Pipeline( steps=[('imputer', SimpleImputer(strategy='constant', fill_value=0))] ) numeric_features = [f for f in self._features if f not in self.categorical_features and f in self.features_to_minimize] categorical_transformer = OneHotEncoder(handle_unknown="ignore", sparse=False) preprocessor_QI_features = ColumnTransformer( transformers=[ ("num", numeric_transformer, numeric_features), ("cat", categorical_transformer, categorical_features), ] ) preprocessor_QI_features.fit(x_QI) # preprocessor to fit data that have features not included in QI (to get accuracy) numeric_features = [f for f in self._features if f not in self.categorical_features] numeric_transformer = Pipeline( steps=[('imputer', SimpleImputer(strategy='constant', fill_value=0))] ) categorical_transformer = OneHotEncoder(handle_unknown="ignore", sparse=False) preprocessor = ColumnTransformer( transformers=[ ("num", numeric_transformer, numeric_features), ("cat", categorical_transformer, self.categorical_features), ] ) preprocessor.fit(X) x_prepared = preprocessor.transform(X_train) if self.train_only_QI: x_prepared = preprocessor_QI_features.transform(X_train_QI) self._preprocessor = preprocessor self.cells_ = {} self.dt_ = DecisionTreeClassifier(random_state=0, min_samples_split=2, min_samples_leaf=1) self.dt_.fit(x_prepared, y_train) self._modify_categorical_features(used_data) x_prepared = pd.DataFrame(x_prepared, columns=self.categorical_data.columns) self._calculate_cells() self._modify_cells() # features that are not from QI should not be part of generalizations for feature in self._features: if feature not in self.features_to_minimize: self._remove_feature_from_cells(self.cells_, self.cells_by_id_, feature) nodes = self._get_nodes_level(0) self._attach_cells_representatives(x_prepared, used_X_train, y_train, nodes) # self.cells_ currently holds the generalization created from the tree leaves self._calculate_generalizations() # apply generalizations to test data x_prepared_test = preprocessor.transform(X_test) if self.train_only_QI: x_prepared_test = preprocessor_QI_features.transform(X_test_QI) x_prepared_test = pd.DataFrame(x_prepared_test, index=X_test.index, columns=self.categorical_data.columns) generalized = self._generalize(X_test, x_prepared_test, nodes, self.cells_, self.cells_by_id_) # check accuracy accuracy = self.estimator.score(preprocessor.transform(generalized), y_test) print('Initial accuracy of model on generalized data, relative to original model predictions ' '(base generalization derived from tree, before improvements): %f' % accuracy) # if accuracy above threshold, improve generalization if accuracy > self.target_accuracy: print('Improving generalizations') level = 1 while accuracy > self.target_accuracy: try: cells_previous_iter = self.cells_ generalization_prev_iter = self.generalizations_ cells_by_id_prev = self.cells_by_id_ nodes = self._get_nodes_level(level) self._calculate_level_cells(level) self._attach_cells_representatives(x_prepared, used_X_train, y_train, nodes) self._calculate_generalizations() generalized = self._generalize(X_test, x_prepared_test, nodes, self.cells_, self.cells_by_id_) accuracy = self.estimator.score(preprocessor.transform(generalized), y_test) # if accuracy passed threshold roll back to previous iteration generalizations if accuracy < self.target_accuracy: self.cells_ = cells_previous_iter self.generalizations_ = generalization_prev_iter self.cells_by_id_ = cells_by_id_prev break else: print('Pruned tree to level: %d, new relative accuracy: %f' % (level, accuracy)) level += 1 except Exception as e: print(e) break # if accuracy below threshold, improve accuracy by removing features from generalization elif accuracy < self.target_accuracy: print('Improving accuracy') while accuracy < self.target_accuracy: removed_feature = self._remove_feature_from_generalization(X_test, x_prepared_test, nodes, y_test, feature_data, accuracy) if removed_feature is None: break self._calculate_generalizations() generalized = self._generalize(X_test, x_prepared_test, nodes, self.cells_, self.cells_by_id_) accuracy = self.estimator.score(preprocessor.transform(generalized), y_test) print('Removed feature: %s, new relative accuracy: %f' % (removed_feature, accuracy)) # self.cells_ currently holds the chosen generalization based on target accuracy # calculate iLoss self.ncp_ = self._calculate_ncp(X_test, self.generalizations_, feature_data) # Return the transformer return self def transform(self, X: Union[np.ndarray, pd.DataFrame]): """ Transforms data records to representative points. Parameters ---------- X : {array-like, sparse-matrix}, shape (n_samples, n_features), If provided as a pandas dataframe, may contain both numeric and categorical data. The input samples. Returns ------- X_transformed : numpy or pandas according to the input type, shape (n_samples, n_features) The array containing the representative values to which each record in ``X`` is mapped. """ # Check if fit has been called msg = 'This %(name)s instance is not initialized yet. ' \ 'Call ‘fit’ or ‘set_params’ with ' \ 'appropriate arguments before using this method.' check_is_fitted(self, ['cells', 'features'], msg=msg) if type(X) == np.ndarray: # Input validation X = check_array(X, accept_sparse=True) self.is_numpy = True X = pd.DataFrame(X, columns=self._features) else: self.is_numpy = False if X.shape[1] != self.n_features_ and self.n_features_ != 0: raise ValueError('Shape of input is different from what was seen' 'in `fit`') if not self._features: self._features = [i for i in range(X.shape[1])] representatives = pd.DataFrame(columns=self._features) # only columns generalized = pd.DataFrame(X, columns=self._features, copy=True) # original data mapped = np.zeros(X.shape[0]) # to mark records we already mapped # iterate over cells (leaves in decision tree) for i in range(len(self.cells_)): # Copy the representatives from the cells into another data structure: # iterate over features in test data for feature in self._features: # if feature has a representative value in the cell and should not # be left untouched, take the representative value if feature in self.cells_[i]['representative'] and \ ('untouched' not in self.cells_[i] or feature not in self.cells_[i]['untouched']): representatives.loc[i, feature] = self.cells_[i]['representative'][feature] # else, drop the feature (removes from representatives columns that # do not have a representative value or should remain untouched) elif feature in representatives.columns.tolist(): representatives = representatives.drop(feature, axis=1) # get the indexes of all records that map to this cell indexes = self._get_record_indexes_for_cell(X, self.cells_[i], mapped) # replace the values in the representative columns with the representative # values (leaves others untouched) if indexes and not representatives.columns.empty: if len(indexes) > 1: replace = pd.concat([representatives.loc[i].to_frame().T] * len(indexes)).reset_index(drop=True) else: replace = representatives.loc[i].to_frame().T.reset_index(drop=True) replace.index = indexes generalized.loc[indexes, representatives.columns] = replace if self.is_numpy: return generalized.to_numpy() return generalized def _get_record_indexes_for_cell(self, X, cell, mapped): indexes = [] for index, row in X.iterrows(): if not mapped.item(index) and self._cell_contains(cell, row, index, mapped): indexes.append(index) return indexes def _cell_contains(self, cell, x, i, mapped): for f in self._features: if f in cell['ranges']: if not self._cell_contains_numeric(f, cell['ranges'][f], x): return False elif f in cell['categories']: if not self._cell_contains_categorical(f, cell['categories'][f], x): return False elif f in cell['untouched']: continue else: raise TypeError("feature " + f + "not found in cell" + cell['id']) # Mark as mapped mapped.itemset(i, 1) return True def _modify_categorical_features(self, X): self.categorical_values = {} self.oneHotVectorFeaturesToFeatures = {} features_to_remove = [] used_features = self._features if self.train_only_QI: used_features = self.features_to_minimize for feature in self.categorical_features: if feature in used_features: try: all_values = X.loc[:, feature] values = list(all_values.unique()) self.categorical_values[feature] = values X[feature] = pd.Categorical(X.loc[:, feature], categories=values, ordered=False) ohe = pd.get_dummies(X[feature], prefix=feature) for oneHotVectorFeature in ohe.columns: self.oneHotVectorFeaturesToFeatures[oneHotVectorFeature] = feature X = pd.concat([X, ohe], axis=1) features_to_remove.append(feature) except KeyError: print("feature " + feature + "not found in training data") self.categorical_data = X.drop(features_to_remove, axis=1) def _cell_contains_numeric(self, f, range, x): i = self._features.index(f) # convert x to ndarray to allow indexing a = np.array(x) value = a.item(i) if range['start']: if value <= range['start']: return False if range['end']: if value > range['end']: return False return True def _cell_contains_categorical(self, f, range, x): i = self._features.index(f) # convert x to ndarray to allow indexing a = np.array(x) value = a.item(i) if value in range: return True return False def _calculate_cells(self): self.cells_by_id_ = {} self.cells_ = self._calculate_cells_recursive(0) def _calculate_cells_recursive(self, node): feature_index = self.dt_.tree_.feature[node] if feature_index == -2: # this is a leaf label = self._calculate_cell_label(node) hist = [int(i) for i in self.dt_.tree_.value[node][0]] cell = {'label': label, 'hist': hist, 'ranges': {}, 'id': int(node)} return [cell] cells = [] feature = self.categorical_data.columns[feature_index] threshold = self.dt_.tree_.threshold[node] left_child = self.dt_.tree_.children_left[node] right_child = self.dt_.tree_.children_right[node] left_child_cells = self._calculate_cells_recursive(left_child) for cell in left_child_cells: if feature not in cell['ranges'].keys(): cell['ranges'][feature] = {'start': None, 'end': None} if cell['ranges'][feature]['end'] is None: cell['ranges'][feature]['end'] = threshold cells.append(cell) self.cells_by_id_[cell['id']] = cell right_child_cells = self._calculate_cells_recursive(right_child) for cell in right_child_cells: if feature not in cell['ranges'].keys(): cell['ranges'][feature] = {'start': None, 'end': None} if cell['ranges'][feature]['start'] is None: cell['ranges'][feature]['start'] = threshold cells.append(cell) self.cells_by_id_[cell['id']] = cell return cells def _calculate_cell_label(self, node): label_hist = self.dt_.tree_.value[node][0] return int(self.dt_.classes_[np.argmax(label_hist)]) def _modify_cells(self): cells = [] features = self.categorical_data.columns for cell in self.cells_: new_cell = {'id': cell['id'], 'label': cell['label'], 'ranges': {}, 'categories': {}, 'hist': cell['hist'], 'representative': None} for feature in features: if feature in self.oneHotVectorFeaturesToFeatures.keys(): # feature is categorical and should be mapped categorical_feature = self.oneHotVectorFeaturesToFeatures[feature] if categorical_feature not in new_cell['categories'].keys(): new_cell['categories'][categorical_feature] = self.categorical_values[ categorical_feature].copy() if feature in cell['ranges'].keys(): categorical_value = feature[len(categorical_feature) + 1:] if cell['ranges'][feature]['start'] is not None: # categorical feature must have this value new_cell['categories'][categorical_feature] = [categorical_value] else: # categorical feature can not have this value if categorical_value in new_cell['categories'][categorical_feature]: new_cell['categories'][categorical_feature].remove(categorical_value) else: if feature in cell['ranges'].keys(): new_cell['ranges'][feature] = cell['ranges'][feature] else: new_cell['ranges'][feature] = {'start': None, 'end': None} cells.append(new_cell) self.cells_by_id_[new_cell['id']] = new_cell self.cells_ = cells def _calculate_level_cells(self, level): if level < 0 or level > self.dt_.get_depth(): raise TypeError("Illegal level %d' % level", level) if level > 0: new_cells = [] new_cells_by_id = {} nodes = self._get_nodes_level(level) if nodes: for node in nodes: if self.dt_.tree_.feature[node] == -2: # leaf node new_cell = self.cells_by_id_[node] else: left_child = self.dt_.tree_.children_left[node] right_child = self.dt_.tree_.children_right[node] left_cell = self.cells_by_id_[left_child] right_cell = self.cells_by_id_[right_child] new_cell = {'id': int(node), 'ranges': {}, 'categories': {}, 'untouched': [], 'label': None, 'representative': None} for feature in left_cell['ranges'].keys(): new_cell['ranges'][feature] = {} new_cell['ranges'][feature]['start'] = left_cell['ranges'][feature]['start'] new_cell['ranges'][feature]['end'] = right_cell['ranges'][feature]['start'] for feature in left_cell['categories'].keys(): new_cell['categories'][feature] = \ list(set(left_cell['categories'][feature]) | set(right_cell['categories'][feature])) for feature in left_cell['untouched']: if feature in right_cell['untouched']: new_cell['untouched'].append(feature) self._calculate_level_cell_label(left_cell, right_cell, new_cell) new_cells.append(new_cell) new_cells_by_id[new_cell['id']] = new_cell self.cells_ = new_cells self.cells_by_id_ = new_cells_by_id # else: nothing to do, stay with previous cells def _calculate_level_cell_label(self, left_cell, right_cell, new_cell): new_cell['hist'] = [x + y for x, y in zip(left_cell['hist'], right_cell['hist'])] new_cell['label'] = int(self.dt_.classes_[np.argmax(new_cell['hist'])]) def _get_nodes_level(self, level): # level = distance from lowest leaf node_depth = np.zeros(shape=self.dt_.tree_.node_count, dtype=np.int64) is_leaves = np.zeros(shape=self.dt_.tree_.node_count, dtype=bool) stack = [(0, -1)] # seed is the root node id and its parent depth while len(stack) > 0: node_id, parent_depth = stack.pop() # depth = distance from root node_depth[node_id] = parent_depth + 1 if self.dt_.tree_.children_left[node_id] != self.dt_.tree_.children_right[node_id]: stack.append((self.dt_.tree_.children_left[node_id], parent_depth + 1)) stack.append((self.dt_.tree_.children_right[node_id], parent_depth + 1)) else: is_leaves[node_id] = True # depth of entire tree max_depth = max(node_depth) # depth of current level depth = max_depth - level # level is higher than root if depth < 0: return None # return all nodes with depth == level or leaves higher than level return [i for i, x in enumerate(node_depth) if x == depth or (x < depth and is_leaves[i])] def _attach_cells_representatives(self, prepared_data, originalTrainFeatures, labelFeature, level_nodes): # prepared data include one hot encoded categorical data, # if there is no categorical data prepared data is original data nodeIds = self._find_sample_nodes(prepared_data, level_nodes) labels_df = pd.DataFrame(labelFeature, columns=['label']) for cell in self.cells_: cell['representative'] = {} # get all rows in cell indexes = [i for i, x in enumerate(nodeIds) if x == cell['id']] original_rows = originalTrainFeatures.iloc[indexes] sample_rows = prepared_data.iloc[indexes] sample_labels = labels_df.iloc[indexes]['label'].values.tolist() # get rows with matching label indexes = [i for i, label in enumerate(sample_labels) if label == cell['label']] match_samples = sample_rows.iloc[indexes] match_rows = original_rows.iloc[indexes] # find the "middle" of the cluster array = match_samples.values # Only works with numpy 1.9.0 and higher!!! median = np.median(array, axis=0) i = 0 min = len(array) min_dist = float("inf") for row in array: dist = distance.euclidean(row, median) if dist < min_dist: min_dist = dist min = i i = i + 1 row = match_rows.iloc[min] for feature in cell['ranges'].keys(): cell['representative'][feature] = row[feature] for feature in cell['categories'].keys(): cell['representative'][feature] = row[feature] def _find_sample_nodes(self, samples, nodes): paths = self.dt_.decision_path(samples).toarray() nodeSet = set(nodes) return [(list(set([i for i, v in enumerate(p) if v == 1]) & nodeSet))[0] for p in paths] def _generalize(self, original_data, prepared_data, level_nodes, cells, cells_by_id): # prepared data include one hot encoded categorical data + QI representatives = pd.DataFrame(columns=self._features) # empty except for columns generalized = pd.DataFrame(prepared_data, columns=self.categorical_data.columns, copy=True) original_data_generalized = pd.DataFrame(original_data, columns=self._features, copy=True) mapping_to_cells = self._map_to_cells(generalized, level_nodes, cells_by_id) # iterate over cells (leaves in decision tree) for i in range(len(cells)): # This code just copies the representatives from the cells into another data structure # iterate over features for feature in self._features: # if feature has a representative value in the cell and should not be left untouched, # take the representative value if feature in cells[i]['representative'] and ('untouched' not in cells[i] or feature not in cells[i]['untouched']): representatives.loc[i, feature] = cells[i]['representative'][feature] # else, drop the feature (removes from representatives columns that do not have a # representative value or should remain untouched) elif feature in representatives.columns.tolist(): representatives = representatives.drop(feature, axis=1) # get the indexes of all records that map to this cell indexes = [j for j in mapping_to_cells if mapping_to_cells[j]['id'] == cells[i]['id']] # replaces the values in the representative columns with the representative values # (leaves others untouched) if indexes and not representatives.columns.empty: if len(indexes) > 1: replace = pd.concat([representatives.loc[i].to_frame().T] * len(indexes)).reset_index(drop=True) else: replace = representatives.loc[i].to_frame().T.reset_index(drop=True) replace.index = indexes replace = pd.DataFrame(replace, indexes, columns=self._features) original_data_generalized.loc[indexes, representatives.columns.tolist()] = replace return original_data_generalized def _map_to_cells(self, samples, nodes, cells_by_id): mapping_to_cells = {} for index, row in samples.iterrows(): cell = self._find_sample_cells([row], nodes, cells_by_id)[0] mapping_to_cells[index] = cell return mapping_to_cells def _find_sample_cells(self, samples, nodes, cells_by_id): node_ids = self._find_sample_nodes(samples, nodes) return [cells_by_id[nodeId] for nodeId in node_ids] def _remove_feature_from_generalization(self, original_data, prepared_data, nodes, labels, feature_data, current_accuracy): # prepared data include one hot encoded categorical data, # if there is no categorical data prepared data is original data feature = self._get_feature_to_remove(original_data, prepared_data, nodes, labels, feature_data, current_accuracy) if feature is None: return None GeneralizeToRepresentative._remove_feature_from_cells(self.cells_, self.cells_by_id_, feature) return feature def _get_feature_to_remove(self, original_data, prepared_data, nodes, labels, feature_data, current_accuracy): # prepared data include one hot encoded categorical data, # if there is no categorical data prepared data is original data # We want to remove features with low iLoss (NCP) and high accuracy gain # (after removing them) ranges = self.generalizations_['ranges'] range_counts = self._find_range_count(original_data, ranges) total = prepared_data.size range_min = sys.float_info.max remove_feature = None categories = self.generalizations['categories'] category_counts = self._find_categories_count(original_data, categories) for feature in ranges.keys(): if feature not in self.generalizations_['untouched']: feature_ncp = self._calc_ncp_numeric(ranges[feature], range_counts[feature], feature_data[feature], total) if feature_ncp > 0: # divide by accuracy gain new_cells = copy.deepcopy(self.cells_) cells_by_id = copy.deepcopy(self.cells_by_id_) GeneralizeToRepresentative._remove_feature_from_cells(new_cells, cells_by_id, feature) generalized = self._generalize(original_data, prepared_data, nodes, new_cells, cells_by_id) accuracy_gain = self.estimator.score(self._preprocessor.transform(generalized), labels) - current_accuracy if accuracy_gain < 0: accuracy_gain = 0 if accuracy_gain != 0: feature_ncp = feature_ncp / accuracy_gain if feature_ncp < range_min: range_min = feature_ncp remove_feature = feature for feature in categories.keys(): if feature not in self.generalizations['untouched']: feature_ncp = self._calc_ncp_categorical(categories[feature], category_counts[feature], feature_data[feature], total) if feature_ncp > 0: # divide by accuracy loss new_cells = copy.deepcopy(self.cells_) cells_by_id = copy.deepcopy(self.cells_by_id_) GeneralizeToRepresentative._remove_feature_from_cells(new_cells, cells_by_id, feature) generalized = self._generalize(original_data, prepared_data, nodes, new_cells, cells_by_id) accuracy_gain = self.estimator.score(self._preprocessor.transform(generalized), labels) - current_accuracy if accuracy_gain < 0: accuracy_gain = 0 if accuracy_gain != 0: feature_ncp = feature_ncp / accuracy_gain if feature_ncp < range_min: range_min = feature_ncp remove_feature = feature print('feature to remove: ' + (str(remove_feature) if remove_feature is not None else 'none')) return remove_feature def _calculate_generalizations(self): self.generalizations_ = {'ranges': GeneralizeToRepresentative._calculate_ranges(self.cells_), 'categories': GeneralizeToRepresentative._calculate_categories(self.cells_), 'untouched': GeneralizeToRepresentative._calculate_untouched(self.cells_)} def _find_range_count(self, samples, ranges): samples_df = pd.DataFrame(samples, columns=self.categorical_data.columns) range_counts = {} last_value = None for r in ranges.keys(): range_counts[r] = [] # if empty list, all samples should be counted if not ranges[r]: range_counts[r].append(samples_df.shape[0]) else: for value in ranges[r]: counter = [item for item in samples_df[r] if int(item) <= value] range_counts[r].append(len(counter)) last_value = value counter = [item for item in samples_df[r] if int(item) <= last_value] range_counts[r].append(len(counter)) return range_counts def _find_categories_count(self, samples, categories): category_counts = {} for c in categories.keys(): category_counts[c] = [] for value in categories[c]: category_counts[c].append(len(samples.loc[samples[c].isin(value)])) return category_counts def _calculate_ncp(self, samples, generalizations, feature_data): # supressed features are already taken care of within _calc_ncp_numeric ranges = generalizations['ranges'] categories = generalizations['categories'] range_counts = self._find_range_count(samples, ranges) category_counts = self._find_categories_count(samples, categories) total = samples.shape[0] total_ncp = 0 total_features = len(generalizations['untouched']) for feature in ranges.keys(): feature_ncp = self._calc_ncp_numeric(ranges[feature], range_counts[feature], feature_data[feature], total) total_ncp = total_ncp + feature_ncp total_features += 1 for feature in categories.keys(): featureNCP = self._calc_ncp_categorical(categories[feature], category_counts[feature], feature_data[feature], total) total_ncp = total_ncp + featureNCP total_features += 1 if total_features == 0: return 0 return total_ncp / total_features @staticmethod def _calculate_ranges(cells): ranges = {} for cell in cells: for feature in [key for key in cell['ranges'].keys() if 'untouched' not in cell or key not in cell['untouched']]: if feature not in ranges.keys(): ranges[feature] = [] if cell['ranges'][feature]['start'] is not None: ranges[feature].append(cell['ranges'][feature]['start']) if cell['ranges'][feature]['end'] is not None: ranges[feature].append(cell['ranges'][feature]['end']) for feature in ranges.keys(): ranges[feature] = list(set(ranges[feature])) ranges[feature].sort() return ranges @staticmethod def _calculate_categories(cells): categories = {} categorical_features_values = GeneralizeToRepresentative._calculate_categorical_features_values(cells) for feature in categorical_features_values.keys(): partitions = [] values = categorical_features_values[feature] assigned = [] for i in range(len(values)): value1 = values[i] if value1 in assigned: continue partition = [value1] assigned.append(value1) for j in range(len(values)): if j <= i: continue value2 = values[j] if GeneralizeToRepresentative._are_inseparable(cells, feature, value1, value2): partition.append(value2) assigned.append(value2) partitions.append(partition) categories[feature] = partitions return categories @staticmethod def _calculate_categorical_features_values(cells): categorical_features_values = {} for cell in cells: for feature in [key for key in cell['categories'].keys() if 'untouched' not in cell or key not in cell['untouched']]: if feature not in categorical_features_values.keys(): categorical_features_values[feature] = [] for value in cell['categories'][feature]: if value not in categorical_features_values[feature]: categorical_features_values[feature].append(value) return categorical_features_values @staticmethod def _are_inseparable(cells, feature, value1, value2): for cell in cells: if feature not in cell['categories'].keys(): continue value1_in = value1 in cell['categories'][feature] value2_in = value2 in cell['categories'][feature] if value1_in != value2_in: return False return True @staticmethod def _calculate_untouched(cells): untouched_lists = [cell['untouched'] if 'untouched' in cell else [] for cell in cells] untouched = set(untouched_lists[0]) untouched = untouched.intersection(*untouched_lists) return list(untouched) @staticmethod def _calc_ncp_categorical(categories, categoryCount, feature_data, total): category_sizes = [len(g) if len(g) > 1 else 0 for g in categories] normalized_category_sizes = [s * n / total for s, n in zip(category_sizes, categoryCount)] average_group_size = sum(normalized_category_sizes) / len(normalized_category_sizes) return average_group_size / feature_data['range'] # number of values in category @staticmethod def _calc_ncp_numeric(feature_range, range_count, feature_data, total): # if there are no ranges, feature is supressed and iLoss is 1 if not feature_range: return 1 # range only contains the split values, need to add min and max value of feature # to enable computing sizes of all ranges new_range = [feature_data['min']] + feature_range + [feature_data['max']] range_sizes = [b - a for a, b in zip(new_range[::1], new_range[1::1])] normalized_range_sizes = [s * n / total for s, n in zip(range_sizes, range_count)] average_range_size = sum(normalized_range_sizes) / len(normalized_range_sizes) return average_range_size / (feature_data['max'] - feature_data['min']) @staticmethod def _remove_feature_from_cells(cells, cells_by_id, feature): for cell in cells: if 'untouched' not in cell: cell['untouched'] = [] if feature in cell['ranges'].keys(): del cell['ranges'][feature] elif feature in cell['categories'].keys(): del cell['categories'][feature] cell['untouched'].append(feature) cells_by_id[cell['id']] = cell.copy()