""" Soft Voting/Majority Rule classifier. This module contains a Soft Voting/Majority Rule classifier for classification estimators. """ # Authors: Sebastian Raschka , # Gilles Louppe # # License: BSD 3 clause import numpy as np import warnings from ..base import ClassifierMixin from ..base import TransformerMixin from ..base import clone from ..preprocessing import LabelEncoder from ..utils._joblib import Parallel, delayed from ..utils.validation import has_fit_parameter, check_is_fitted from ..utils.metaestimators import _BaseComposition from ..utils import Bunch def _parallel_fit_estimator(estimator, X, y, sample_weight=None): """Private function used to fit an estimator within a job.""" if sample_weight is not None: estimator.fit(X, y, sample_weight=sample_weight) else: estimator.fit(X, y) return estimator class VotingClassifier(_BaseComposition, ClassifierMixin, TransformerMixin): """Soft Voting/Majority Rule classifier for unfitted estimators. .. versionadded:: 0.17 Read more in the :ref:`User Guide `. Parameters ---------- estimators : list of (string, estimator) tuples Invoking the ``fit`` method on the ``VotingClassifier`` will fit clones of those original estimators that will be stored in the class attribute ``self.estimators_``. An estimator can be set to `None` using ``set_params``. voting : str, {'hard', 'soft'} (default='hard') If 'hard', uses predicted class labels for majority rule voting. Else if 'soft', predicts the class label based on the argmax of the sums of the predicted probabilities, which is recommended for an ensemble of well-calibrated classifiers. weights : array-like, shape = [n_classifiers], optional (default=`None`) Sequence of weights (`float` or `int`) to weight the occurrences of predicted class labels (`hard` voting) or class probabilities before averaging (`soft` voting). Uses uniform weights if `None`. n_jobs : int or None, optional (default=None) The number of jobs to run in parallel for ``fit``. ``None`` means 1 unless in a :obj:`joblib.parallel_backend` context. ``-1`` means using all processors. See :term:`Glossary ` for more details. flatten_transform : bool, optional (default=None) Affects shape of transform output only when voting='soft' If voting='soft' and flatten_transform=True, transform method returns matrix with shape (n_samples, n_classifiers * n_classes). If flatten_transform=False, it returns (n_classifiers, n_samples, n_classes). Attributes ---------- estimators_ : list of classifiers The collection of fitted sub-estimators as defined in ``estimators`` that are not `None`. named_estimators_ : Bunch object, a dictionary with attribute access Attribute to access any fitted sub-estimators by name. .. versionadded:: 0.20 classes_ : array-like, shape = [n_predictions] The classes labels. Examples -------- >>> import numpy as np >>> from sklearn.linear_model import LogisticRegression >>> from sklearn.naive_bayes import GaussianNB >>> from sklearn.ensemble import RandomForestClassifier, VotingClassifier >>> clf1 = LogisticRegression(solver='lbfgs', multi_class='multinomial', ... random_state=1) >>> clf2 = RandomForestClassifier(n_estimators=50, random_state=1) >>> clf3 = GaussianNB() >>> X = np.array([[-1, -1], [-2, -1], [-3, -2], [1, 1], [2, 1], [3, 2]]) >>> y = np.array([1, 1, 1, 2, 2, 2]) >>> eclf1 = VotingClassifier(estimators=[ ... ('lr', clf1), ('rf', clf2), ('gnb', clf3)], voting='hard') >>> eclf1 = eclf1.fit(X, y) >>> print(eclf1.predict(X)) [1 1 1 2 2 2] >>> np.array_equal(eclf1.named_estimators_.lr.predict(X), ... eclf1.named_estimators_['lr'].predict(X)) True >>> eclf2 = VotingClassifier(estimators=[ ... ('lr', clf1), ('rf', clf2), ('gnb', clf3)], ... voting='soft') >>> eclf2 = eclf2.fit(X, y) >>> print(eclf2.predict(X)) [1 1 1 2 2 2] >>> eclf3 = VotingClassifier(estimators=[ ... ('lr', clf1), ('rf', clf2), ('gnb', clf3)], ... voting='soft', weights=[2,1,1], ... flatten_transform=True) >>> eclf3 = eclf3.fit(X, y) >>> print(eclf3.predict(X)) [1 1 1 2 2 2] >>> print(eclf3.transform(X).shape) (6, 6) """ def __init__(self, estimators, voting='hard', weights=None, n_jobs=None, flatten_transform=None): self.estimators = estimators self.voting = voting self.weights = weights self.n_jobs = n_jobs self.flatten_transform = flatten_transform @property def named_estimators(self): return Bunch(**dict(self.estimators)) def fit(self, X, y, sample_weight=None): """ Fit the estimators. Parameters ---------- X : {array-like, sparse matrix}, shape = [n_samples, n_features] Training vectors, where n_samples is the number of samples and n_features is the number of features. y : array-like, shape = [n_samples] Target values. sample_weight : array-like, shape = [n_samples] or None Sample weights. If None, then samples are equally weighted. Note that this is supported only if all underlying estimators support sample weights. Returns ------- self : object """ if isinstance(y, np.ndarray) and len(y.shape) > 1 and y.shape[1] > 1: raise NotImplementedError('Multilabel and multi-output' ' classification is not supported.') if self.voting not in ('soft', 'hard'): raise ValueError("Voting must be 'soft' or 'hard'; got (voting=%r)" % self.voting) if self.estimators is None or len(self.estimators) == 0: raise AttributeError('Invalid `estimators` attribute, `estimators`' ' should be a list of (string, estimator)' ' tuples') if (self.weights is not None and len(self.weights) != len(self.estimators)): raise ValueError('Number of classifiers and weights must be equal' '; got %d weights, %d estimators' % (len(self.weights), len(self.estimators))) if sample_weight is not None: for name, step in self.estimators: if not has_fit_parameter(step, 'sample_weight'): raise ValueError('Underlying estimator \'%s\' does not' ' support sample weights.' % name) names, clfs = zip(*self.estimators) self._validate_names(names) n_isnone = np.sum([clf is None for _, clf in self.estimators]) if n_isnone == len(self.estimators): raise ValueError('All estimators are None. At least one is ' 'required to be a classifier!') self.le_ = LabelEncoder().fit(y) self.classes_ = self.le_.classes_ self.estimators_ = [] transformed_y = self.le_.transform(y) self.estimators_ = Parallel(n_jobs=self.n_jobs)( delayed(_parallel_fit_estimator)(clone(clf), X, transformed_y, sample_weight=sample_weight) for clf in clfs if clf is not None) self.named_estimators_ = Bunch(**dict()) for k, e in zip(self.estimators, self.estimators_): self.named_estimators_[k[0]] = e return self @property def _weights_not_none(self): """Get the weights of not `None` estimators""" if self.weights is None: return None return [w for est, w in zip(self.estimators, self.weights) if est[1] is not None] def predict(self, X): """ Predict class labels for X. Parameters ---------- X : {array-like, sparse matrix}, shape = [n_samples, n_features] Training vectors, where n_samples is the number of samples and n_features is the number of features. Returns ---------- maj : array-like, shape = [n_samples] Predicted class labels. """ check_is_fitted(self, 'estimators_') if self.voting == 'soft': maj = np.argmax(self.predict_proba(X), axis=1) else: # 'hard' voting predictions = self._predict(X) maj = np.apply_along_axis( lambda x: np.argmax( np.bincount(x, weights=self._weights_not_none)), axis=1, arr=predictions) maj = self.le_.inverse_transform(maj) return maj def _collect_probas(self, X): """Collect results from clf.predict calls. """ return np.asarray([clf.predict_proba(X) for clf in self.estimators_]) def _predict_proba(self, X): """Predict class probabilities for X in 'soft' voting """ if self.voting == 'hard': raise AttributeError("predict_proba is not available when" " voting=%r" % self.voting) check_is_fitted(self, 'estimators_') avg = np.average(self._collect_probas(X), axis=0, weights=self._weights_not_none) return avg @property def predict_proba(self): """Compute probabilities of possible outcomes for samples in X. Parameters ---------- X : {array-like, sparse matrix}, shape = [n_samples, n_features] Training vectors, where n_samples is the number of samples and n_features is the number of features. Returns ---------- avg : array-like, shape = [n_samples, n_classes] Weighted average probability for each class per sample. """ return self._predict_proba def transform(self, X): """Return class labels or probabilities for X for each estimator. Parameters ---------- X : {array-like, sparse matrix}, shape = [n_samples, n_features] Training vectors, where n_samples is the number of samples and n_features is the number of features. Returns ------- probabilities_or_labels If `voting='soft'` and `flatten_transform=True`: returns array-like of shape (n_classifiers, n_samples * n_classes), being class probabilities calculated by each classifier. If `voting='soft' and `flatten_transform=False`: array-like of shape (n_classifiers, n_samples, n_classes) If `voting='hard'`: array-like of shape (n_samples, n_classifiers), being class labels predicted by each classifier. """ check_is_fitted(self, 'estimators_') if self.voting == 'soft': probas = self._collect_probas(X) if self.flatten_transform is None: warnings.warn("'flatten_transform' default value will be " "changed to True in 0.21. " "To silence this warning you may" " explicitly set flatten_transform=False.", DeprecationWarning) return probas elif not self.flatten_transform: return probas else: return np.hstack(probas) else: return self._predict(X) def set_params(self, **params): """ Setting the parameters for the voting classifier Valid parameter keys can be listed with get_params(). Parameters ---------- **params : keyword arguments Specific parameters using e.g. set_params(parameter_name=new_value) In addition, to setting the parameters of the ``VotingClassifier``, the individual classifiers of the ``VotingClassifier`` can also be set or replaced by setting them to None. Examples -------- # In this example, the RandomForestClassifier is removed clf1 = LogisticRegression() clf2 = RandomForestClassifier() eclf = VotingClassifier(estimators=[('lr', clf1), ('rf', clf2)] eclf.set_params(rf=None) """ super(VotingClassifier, self)._set_params('estimators', **params) return self def get_params(self, deep=True): """ Get the parameters of the VotingClassifier Parameters ---------- deep : bool Setting it to True gets the various classifiers and the parameters of the classifiers as well """ return super(VotingClassifier, self)._get_params('estimators', deep=deep) def _predict(self, X): """Collect results from clf.predict calls. """ return np.asarray([clf.predict(X) for clf in self.estimators_]).T