from __future__ import print_function import numpy as np import scipy.sparse as sp import warnings from abc import ABCMeta, abstractmethod from . import libsvm, liblinear from . import libsvm_sparse from ..base import BaseEstimator, ClassifierMixin from ..preprocessing import LabelEncoder from ..utils.multiclass import _ovr_decision_function from ..utils import check_array, check_consistent_length, check_random_state from ..utils import column_or_1d, check_X_y from ..utils import compute_class_weight, deprecated from ..utils.extmath import safe_sparse_dot from ..utils.validation import check_is_fitted from ..utils.multiclass import check_classification_targets from ..externals import six from ..exceptions import ChangedBehaviorWarning from ..exceptions import ConvergenceWarning from ..exceptions import NotFittedError LIBSVM_IMPL = ['c_svc', 'nu_svc', 'one_class', 'epsilon_svr', 'nu_svr'] def _one_vs_one_coef(dual_coef, n_support, support_vectors): """Generate primal coefficients from dual coefficients for the one-vs-one multi class LibSVM in the case of a linear kernel.""" # get 1vs1 weights for all n*(n-1) classifiers. # this is somewhat messy. # shape of dual_coef_ is nSV * (n_classes -1) # see docs for details n_class = dual_coef.shape[0] + 1 # XXX we could do preallocation of coef but # would have to take care in the sparse case coef = [] sv_locs = np.cumsum(np.hstack([[0], n_support])) for class1 in range(n_class): # SVs for class1: sv1 = support_vectors[sv_locs[class1]:sv_locs[class1 + 1], :] for class2 in range(class1 + 1, n_class): # SVs for class1: sv2 = support_vectors[sv_locs[class2]:sv_locs[class2 + 1], :] # dual coef for class1 SVs: alpha1 = dual_coef[class2 - 1, sv_locs[class1]:sv_locs[class1 + 1]] # dual coef for class2 SVs: alpha2 = dual_coef[class1, sv_locs[class2]:sv_locs[class2 + 1]] # build weight for class1 vs class2 coef.append(safe_sparse_dot(alpha1, sv1) + safe_sparse_dot(alpha2, sv2)) return coef class BaseLibSVM(six.with_metaclass(ABCMeta, BaseEstimator)): """Base class for estimators that use libsvm as backing library This implements support vector machine classification and regression. Parameter documentation is in the derived `SVC` class. """ # The order of these must match the integer values in LibSVM. # XXX These are actually the same in the dense case. Need to factor # this out. _sparse_kernels = ["linear", "poly", "rbf", "sigmoid", "precomputed"] @abstractmethod def __init__(self, impl, kernel, degree, gamma, coef0, tol, C, nu, epsilon, shrinking, probability, cache_size, class_weight, verbose, max_iter, random_state): if impl not in LIBSVM_IMPL: # pragma: no cover raise ValueError("impl should be one of %s, %s was given" % ( LIBSVM_IMPL, impl)) if gamma == 0: msg = ("The gamma value of 0.0 is invalid. Use 'auto' to set" " gamma to a value of 1 / n_features.") raise ValueError(msg) self._impl = impl self.kernel = kernel self.degree = degree self.gamma = gamma self.coef0 = coef0 self.tol = tol self.C = C self.nu = nu self.epsilon = epsilon self.shrinking = shrinking self.probability = probability self.cache_size = cache_size self.class_weight = class_weight self.verbose = verbose self.max_iter = max_iter self.random_state = random_state @property def _pairwise(self): # Used by cross_val_score. kernel = self.kernel return kernel == "precomputed" or callable(kernel) def fit(self, X, y, sample_weight=None): """Fit the SVM model according to the given training data. 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. For kernel="precomputed", the expected shape of X is (n_samples, n_samples). y : array-like, shape (n_samples,) Target values (class labels in classification, real numbers in regression) sample_weight : array-like, shape (n_samples,) Per-sample weights. Rescale C per sample. Higher weights force the classifier to put more emphasis on these points. Returns ------- self : object Returns self. Notes ------ If X and y are not C-ordered and contiguous arrays of np.float64 and X is not a scipy.sparse.csr_matrix, X and/or y may be copied. If X is a dense array, then the other methods will not support sparse matrices as input. """ rnd = check_random_state(self.random_state) sparse = sp.isspmatrix(X) if sparse and self.kernel == "precomputed": raise TypeError("Sparse precomputed kernels are not supported.") self._sparse = sparse and not callable(self.kernel) X, y = check_X_y(X, y, dtype=np.float64, order='C', accept_sparse='csr') y = self._validate_targets(y) sample_weight = np.asarray([] if sample_weight is None else sample_weight, dtype=np.float64) solver_type = LIBSVM_IMPL.index(self._impl) # input validation if solver_type != 2 and X.shape[0] != y.shape[0]: raise ValueError("X and y have incompatible shapes.\n" + "X has %s samples, but y has %s." % (X.shape[0], y.shape[0])) if self.kernel == "precomputed" and X.shape[0] != X.shape[1]: raise ValueError("X.shape[0] should be equal to X.shape[1]") if sample_weight.shape[0] > 0 and sample_weight.shape[0] != X.shape[0]: raise ValueError("sample_weight and X have incompatible shapes: " "%r vs %r\n" "Note: Sparse matrices cannot be indexed w/" "boolean masks (use `indices=True` in CV)." % (sample_weight.shape, X.shape)) if self.gamma == 'auto': self._gamma = 1.0 / X.shape[1] else: self._gamma = self.gamma kernel = self.kernel if callable(kernel): kernel = 'precomputed' fit = self._sparse_fit if self._sparse else self._dense_fit if self.verbose: # pragma: no cover print('[LibSVM]', end='') seed = rnd.randint(np.iinfo('i').max) fit(X, y, sample_weight, solver_type, kernel, random_seed=seed) # see comment on the other call to np.iinfo in this file self.shape_fit_ = X.shape # In binary case, we need to flip the sign of coef, intercept and # decision function. Use self._intercept_ and self._dual_coef_ internally. self._intercept_ = self.intercept_.copy() self._dual_coef_ = self.dual_coef_ if self._impl in ['c_svc', 'nu_svc'] and len(self.classes_) == 2: self.intercept_ *= -1 self.dual_coef_ = -self.dual_coef_ return self def _validate_targets(self, y): """Validation of y and class_weight. Default implementation for SVR and one-class; overridden in BaseSVC. """ # XXX this is ugly. # Regression models should not have a class_weight_ attribute. self.class_weight_ = np.empty(0) return column_or_1d(y, warn=True).astype(np.float64) def _warn_from_fit_status(self): assert self.fit_status_ in (0, 1) if self.fit_status_ == 1: warnings.warn('Solver terminated early (max_iter=%i).' ' Consider pre-processing your data with' ' StandardScaler or MinMaxScaler.' % self.max_iter, ConvergenceWarning) def _dense_fit(self, X, y, sample_weight, solver_type, kernel, random_seed): if callable(self.kernel): # you must store a reference to X to compute the kernel in predict # TODO: add keyword copy to copy on demand self.__Xfit = X X = self._compute_kernel(X) if X.shape[0] != X.shape[1]: raise ValueError("X.shape[0] should be equal to X.shape[1]") libsvm.set_verbosity_wrap(self.verbose) if six.PY2: # In python2 ensure kernel is ascii bytes to prevent a TypeError if isinstance(kernel, six.types.UnicodeType): kernel = str(kernel) if six.PY3: # In python3 ensure kernel is utf8 unicode to prevent a TypeError if isinstance(kernel, bytes): kernel = str(kernel, 'utf8') # we don't pass **self.get_params() to allow subclasses to # add other parameters to __init__ self.support_, self.support_vectors_, self.n_support_, \ self.dual_coef_, self.intercept_, self.probA_, \ self.probB_, self.fit_status_ = libsvm.fit( X, y, svm_type=solver_type, sample_weight=sample_weight, class_weight=self.class_weight_, kernel=kernel, C=self.C, nu=self.nu, probability=self.probability, degree=self.degree, shrinking=self.shrinking, tol=self.tol, cache_size=self.cache_size, coef0=self.coef0, gamma=self._gamma, epsilon=self.epsilon, max_iter=self.max_iter, random_seed=random_seed) self._warn_from_fit_status() def _sparse_fit(self, X, y, sample_weight, solver_type, kernel, random_seed): X.data = np.asarray(X.data, dtype=np.float64, order='C') X.sort_indices() kernel_type = self._sparse_kernels.index(kernel) libsvm_sparse.set_verbosity_wrap(self.verbose) self.support_, self.support_vectors_, dual_coef_data, \ self.intercept_, self.n_support_, \ self.probA_, self.probB_, self.fit_status_ = \ libsvm_sparse.libsvm_sparse_train( X.shape[1], X.data, X.indices, X.indptr, y, solver_type, kernel_type, self.degree, self._gamma, self.coef0, self.tol, self.C, self.class_weight_, sample_weight, self.nu, self.cache_size, self.epsilon, int(self.shrinking), int(self.probability), self.max_iter, random_seed) self._warn_from_fit_status() if hasattr(self, "classes_"): n_class = len(self.classes_) - 1 else: # regression n_class = 1 n_SV = self.support_vectors_.shape[0] dual_coef_indices = np.tile(np.arange(n_SV), n_class) dual_coef_indptr = np.arange(0, dual_coef_indices.size + 1, dual_coef_indices.size / n_class) self.dual_coef_ = sp.csr_matrix( (dual_coef_data, dual_coef_indices, dual_coef_indptr), (n_class, n_SV)) def predict(self, X): """Perform regression on samples in X. For an one-class model, +1 or -1 is returned. Parameters ---------- X : {array-like, sparse matrix}, shape (n_samples, n_features) For kernel="precomputed", the expected shape of X is (n_samples_test, n_samples_train). Returns ------- y_pred : array, shape (n_samples,) """ X = self._validate_for_predict(X) predict = self._sparse_predict if self._sparse else self._dense_predict return predict(X) def _dense_predict(self, X): n_samples, n_features = X.shape X = self._compute_kernel(X) if X.ndim == 1: X = check_array(X, order='C') kernel = self.kernel if callable(self.kernel): kernel = 'precomputed' if X.shape[1] != self.shape_fit_[0]: raise ValueError("X.shape[1] = %d should be equal to %d, " "the number of samples at training time" % (X.shape[1], self.shape_fit_[0])) svm_type = LIBSVM_IMPL.index(self._impl) return libsvm.predict( X, self.support_, self.support_vectors_, self.n_support_, self._dual_coef_, self._intercept_, self.probA_, self.probB_, svm_type=svm_type, kernel=kernel, degree=self.degree, coef0=self.coef0, gamma=self._gamma, cache_size=self.cache_size) def _sparse_predict(self, X): # Precondition: X is a csr_matrix of dtype np.float64. kernel = self.kernel if callable(kernel): kernel = 'precomputed' kernel_type = self._sparse_kernels.index(kernel) C = 0.0 # C is not useful here return libsvm_sparse.libsvm_sparse_predict( X.data, X.indices, X.indptr, self.support_vectors_.data, self.support_vectors_.indices, self.support_vectors_.indptr, self._dual_coef_.data, self._intercept_, LIBSVM_IMPL.index(self._impl), kernel_type, self.degree, self._gamma, self.coef0, self.tol, C, self.class_weight_, self.nu, self.epsilon, self.shrinking, self.probability, self.n_support_, self.probA_, self.probB_) def _compute_kernel(self, X): """Return the data transformed by a callable kernel""" if callable(self.kernel): # in the case of precomputed kernel given as a function, we # have to compute explicitly the kernel matrix kernel = self.kernel(X, self.__Xfit) if sp.issparse(kernel): kernel = kernel.toarray() X = np.asarray(kernel, dtype=np.float64, order='C') return X @deprecated(" and will be removed in 0.19") def decision_function(self, X): """Distance of the samples X to the separating hyperplane. Parameters ---------- X : array-like, shape (n_samples, n_features) For kernel="precomputed", the expected shape of X is [n_samples_test, n_samples_train]. Returns ------- X : array-like, shape (n_samples, n_class * (n_class-1) / 2) Returns the decision function of the sample for each class in the model. """ return self._decision_function(X) def _decision_function(self, X): """Distance of the samples X to the separating hyperplane. Parameters ---------- X : array-like, shape (n_samples, n_features) Returns ------- X : array-like, shape (n_samples, n_class * (n_class-1) / 2) Returns the decision function of the sample for each class in the model. """ # NOTE: _validate_for_predict contains check for is_fitted # hence must be placed before any other attributes are used. X = self._validate_for_predict(X) X = self._compute_kernel(X) if self._sparse: dec_func = self._sparse_decision_function(X) else: dec_func = self._dense_decision_function(X) # In binary case, we need to flip the sign of coef, intercept and # decision function. if self._impl in ['c_svc', 'nu_svc'] and len(self.classes_) == 2: return -dec_func.ravel() return dec_func def _dense_decision_function(self, X): X = check_array(X, dtype=np.float64, order="C") kernel = self.kernel if callable(kernel): kernel = 'precomputed' return libsvm.decision_function( X, self.support_, self.support_vectors_, self.n_support_, self._dual_coef_, self._intercept_, self.probA_, self.probB_, svm_type=LIBSVM_IMPL.index(self._impl), kernel=kernel, degree=self.degree, cache_size=self.cache_size, coef0=self.coef0, gamma=self._gamma) def _sparse_decision_function(self, X): X.data = np.asarray(X.data, dtype=np.float64, order='C') kernel = self.kernel if hasattr(kernel, '__call__'): kernel = 'precomputed' kernel_type = self._sparse_kernels.index(kernel) return libsvm_sparse.libsvm_sparse_decision_function( X.data, X.indices, X.indptr, self.support_vectors_.data, self.support_vectors_.indices, self.support_vectors_.indptr, self._dual_coef_.data, self._intercept_, LIBSVM_IMPL.index(self._impl), kernel_type, self.degree, self._gamma, self.coef0, self.tol, self.C, self.class_weight_, self.nu, self.epsilon, self.shrinking, self.probability, self.n_support_, self.probA_, self.probB_) def _validate_for_predict(self, X): check_is_fitted(self, 'support_') X = check_array(X, accept_sparse='csr', dtype=np.float64, order="C") if self._sparse and not sp.isspmatrix(X): X = sp.csr_matrix(X) if self._sparse: X.sort_indices() if sp.issparse(X) and not self._sparse and not callable(self.kernel): raise ValueError( "cannot use sparse input in %r trained on dense data" % type(self).__name__) n_samples, n_features = X.shape if self.kernel == "precomputed": if X.shape[1] != self.shape_fit_[0]: raise ValueError("X.shape[1] = %d should be equal to %d, " "the number of samples at training time" % (X.shape[1], self.shape_fit_[0])) elif n_features != self.shape_fit_[1]: raise ValueError("X.shape[1] = %d should be equal to %d, " "the number of features at training time" % (n_features, self.shape_fit_[1])) return X @property def coef_(self): if self.kernel != 'linear': raise ValueError('coef_ is only available when using a ' 'linear kernel') coef = self._get_coef() # coef_ being a read-only property, it's better to mark the value as # immutable to avoid hiding potential bugs for the unsuspecting user. if sp.issparse(coef): # sparse matrix do not have global flags coef.data.flags.writeable = False else: # regular dense array coef.flags.writeable = False return coef def _get_coef(self): return safe_sparse_dot(self._dual_coef_, self.support_vectors_) class BaseSVC(six.with_metaclass(ABCMeta, BaseLibSVM, ClassifierMixin)): """ABC for LibSVM-based classifiers.""" @abstractmethod def __init__(self, impl, kernel, degree, gamma, coef0, tol, C, nu, shrinking, probability, cache_size, class_weight, verbose, max_iter, decision_function_shape, random_state): self.decision_function_shape = decision_function_shape super(BaseSVC, self).__init__( impl=impl, kernel=kernel, degree=degree, gamma=gamma, coef0=coef0, tol=tol, C=C, nu=nu, epsilon=0., shrinking=shrinking, probability=probability, cache_size=cache_size, class_weight=class_weight, verbose=verbose, max_iter=max_iter, random_state=random_state) def _validate_targets(self, y): y_ = column_or_1d(y, warn=True) check_classification_targets(y) cls, y = np.unique(y_, return_inverse=True) self.class_weight_ = compute_class_weight(self.class_weight, cls, y_) if len(cls) < 2: raise ValueError( "The number of classes has to be greater than one; got %d" % len(cls)) self.classes_ = cls return np.asarray(y, dtype=np.float64, order='C') def decision_function(self, X): """Distance of the samples X to the separating hyperplane. Parameters ---------- X : array-like, shape (n_samples, n_features) Returns ------- X : array-like, shape (n_samples, n_classes * (n_classes-1) / 2) Returns the decision function of the sample for each class in the model. If decision_function_shape='ovr', the shape is (n_samples, n_classes) """ dec = self._decision_function(X) if self.decision_function_shape is None and len(self.classes_) > 2: warnings.warn("The decision_function_shape default value will " "change from 'ovo' to 'ovr' in 0.19. This will change " "the shape of the decision function returned by " "SVC.", ChangedBehaviorWarning) if self.decision_function_shape == 'ovr' and len(self.classes_) > 2: return _ovr_decision_function(dec < 0, dec, len(self.classes_)) return dec def predict(self, X): """Perform classification on samples in X. For an one-class model, +1 or -1 is returned. Parameters ---------- X : {array-like, sparse matrix}, shape (n_samples, n_features) For kernel="precomputed", the expected shape of X is [n_samples_test, n_samples_train] Returns ------- y_pred : array, shape (n_samples,) Class labels for samples in X. """ y = super(BaseSVC, self).predict(X) return self.classes_.take(np.asarray(y, dtype=np.intp)) # Hacky way of getting predict_proba to raise an AttributeError when # probability=False using properties. Do not use this in new code; when # probabilities are not available depending on a setting, introduce two # estimators. def _check_proba(self): if not self.probability: raise AttributeError("predict_proba is not available when " " probability=False") if self._impl not in ('c_svc', 'nu_svc'): raise AttributeError("predict_proba only implemented for SVC" " and NuSVC") @property def predict_proba(self): """Compute probabilities of possible outcomes for samples in X. The model need to have probability information computed at training time: fit with attribute `probability` set to True. Parameters ---------- X : array-like, shape (n_samples, n_features) For kernel="precomputed", the expected shape of X is [n_samples_test, n_samples_train] Returns ------- T : array-like, shape (n_samples, n_classes) Returns the probability of the sample for each class in the model. The columns correspond to the classes in sorted order, as they appear in the attribute `classes_`. Notes ----- The probability model is created using cross validation, so the results can be slightly different than those obtained by predict. Also, it will produce meaningless results on very small datasets. """ self._check_proba() return self._predict_proba def _predict_proba(self, X): X = self._validate_for_predict(X) if self.probA_.size == 0 or self.probB_.size == 0: raise NotFittedError("predict_proba is not available when fitted " "with probability=False") pred_proba = (self._sparse_predict_proba if self._sparse else self._dense_predict_proba) return pred_proba(X) @property def predict_log_proba(self): """Compute log probabilities of possible outcomes for samples in X. The model need to have probability information computed at training time: fit with attribute `probability` set to True. Parameters ---------- X : array-like, shape (n_samples, n_features) For kernel="precomputed", the expected shape of X is [n_samples_test, n_samples_train] Returns ------- T : array-like, shape (n_samples, n_classes) Returns the log-probabilities of the sample for each class in the model. The columns correspond to the classes in sorted order, as they appear in the attribute `classes_`. Notes ----- The probability model is created using cross validation, so the results can be slightly different than those obtained by predict. Also, it will produce meaningless results on very small datasets. """ self._check_proba() return self._predict_log_proba def _predict_log_proba(self, X): return np.log(self.predict_proba(X)) def _dense_predict_proba(self, X): X = self._compute_kernel(X) kernel = self.kernel if callable(kernel): kernel = 'precomputed' svm_type = LIBSVM_IMPL.index(self._impl) pprob = libsvm.predict_proba( X, self.support_, self.support_vectors_, self.n_support_, self._dual_coef_, self._intercept_, self.probA_, self.probB_, svm_type=svm_type, kernel=kernel, degree=self.degree, cache_size=self.cache_size, coef0=self.coef0, gamma=self._gamma) return pprob def _sparse_predict_proba(self, X): X.data = np.asarray(X.data, dtype=np.float64, order='C') kernel = self.kernel if callable(kernel): kernel = 'precomputed' kernel_type = self._sparse_kernels.index(kernel) return libsvm_sparse.libsvm_sparse_predict_proba( X.data, X.indices, X.indptr, self.support_vectors_.data, self.support_vectors_.indices, self.support_vectors_.indptr, self._dual_coef_.data, self._intercept_, LIBSVM_IMPL.index(self._impl), kernel_type, self.degree, self._gamma, self.coef0, self.tol, self.C, self.class_weight_, self.nu, self.epsilon, self.shrinking, self.probability, self.n_support_, self.probA_, self.probB_) def _get_coef(self): if self.dual_coef_.shape[0] == 1: # binary classifier coef = safe_sparse_dot(self.dual_coef_, self.support_vectors_) else: # 1vs1 classifier coef = _one_vs_one_coef(self.dual_coef_, self.n_support_, self.support_vectors_) if sp.issparse(coef[0]): coef = sp.vstack(coef).tocsr() else: coef = np.vstack(coef) return coef def _get_liblinear_solver_type(multi_class, penalty, loss, dual): """Find the liblinear magic number for the solver. This number depends on the values of the following attributes: - multi_class - penalty - loss - dual The same number is also internally used by LibLinear to determine which solver to use. """ # nested dicts containing level 1: available loss functions, # level2: available penalties for the given loss function, # level3: wether the dual solver is available for the specified # combination of loss function and penalty _solver_type_dict = { 'logistic_regression': { 'l1': {False: 6}, 'l2': {False: 0, True: 7}}, 'hinge': { 'l2': {True: 3}}, 'squared_hinge': { 'l1': {False: 5}, 'l2': {False: 2, True: 1}}, 'epsilon_insensitive': { 'l2': {True: 13}}, 'squared_epsilon_insensitive': { 'l2': {False: 11, True: 12}}, 'crammer_singer': 4 } if multi_class == 'crammer_singer': return _solver_type_dict[multi_class] elif multi_class != 'ovr': raise ValueError("`multi_class` must be one of `ovr`, " "`crammer_singer`, got %r" % multi_class) _solver_pen = _solver_type_dict.get(loss, None) if _solver_pen is None: error_string = ("loss='%s' is not supported" % loss) else: _solver_dual = _solver_pen.get(penalty, None) if _solver_dual is None: error_string = ("The combination of penalty='%s' " "and loss='%s' is not supported" % (penalty, loss)) else: solver_num = _solver_dual.get(dual, None) if solver_num is None: error_string = ("The combination of penalty='%s' and " "loss='%s' are not supported when dual=%s" % (penalty, loss, dual)) else: return solver_num raise ValueError('Unsupported set of arguments: %s, ' 'Parameters: penalty=%r, loss=%r, dual=%r' % (error_string, penalty, loss, dual)) def _fit_liblinear(X, y, C, fit_intercept, intercept_scaling, class_weight, penalty, dual, verbose, max_iter, tol, random_state=None, multi_class='ovr', loss='logistic_regression', epsilon=0.1, sample_weight=None): """Used by Logistic Regression (and CV) and LinearSVC. Preprocessing is done in this function before supplying it to liblinear. Parameters ---------- X : {array-like, sparse matrix}, shape (n_samples, n_features) Training vector, where n_samples in the number of samples and n_features is the number of features. y : array-like, shape (n_samples,) Target vector relative to X C : float Inverse of cross-validation parameter. Lower the C, the more the penalization. fit_intercept : bool Whether or not to fit the intercept, that is to add a intercept term to the decision function. intercept_scaling : float LibLinear internally penalizes the intercept and this term is subject to regularization just like the other terms of the feature vector. In order to avoid this, one should increase the intercept_scaling. such that the feature vector becomes [x, intercept_scaling]. class_weight : {dict, 'balanced'}, optional Weights associated with classes in the form ``{class_label: weight}``. If not given, all classes are supposed to have weight one. For multi-output problems, a list of dicts can be provided in the same order as the columns of y. The "balanced" mode uses the values of y to automatically adjust weights inversely proportional to class frequencies in the input data as ``n_samples / (n_classes * np.bincount(y))`` penalty : str, {'l1', 'l2'} The norm of the penalty used in regularization. dual : bool Dual or primal formulation, verbose : int Set verbose to any positive number for verbosity. max_iter : int Number of iterations. tol : float Stopping condition. random_state : int seed, RandomState instance, or None (default) The seed of the pseudo random number generator to use when shuffling the data. multi_class : str, {'ovr', 'crammer_singer'} `ovr` trains n_classes one-vs-rest classifiers, while `crammer_singer` optimizes a joint objective over all classes. While `crammer_singer` is interesting from an theoretical perspective as it is consistent it is seldom used in practice and rarely leads to better accuracy and is more expensive to compute. If `crammer_singer` is chosen, the options loss, penalty and dual will be ignored. loss : str, {'logistic_regression', 'hinge', 'squared_hinge', 'epsilon_insensitive', 'squared_epsilon_insensitive} The loss function used to fit the model. epsilon : float, optional (default=0.1) Epsilon parameter in the epsilon-insensitive loss function. Note that the value of this parameter depends on the scale of the target variable y. If unsure, set epsilon=0. sample_weight: array-like, optional Weights assigned to each sample. Returns ------- coef_ : ndarray, shape (n_features, n_features + 1) The coefficient vector got by minimizing the objective function. intercept_ : float The intercept term added to the vector. n_iter_ : int Maximum number of iterations run across all classes. """ if loss not in ['epsilon_insensitive', 'squared_epsilon_insensitive']: enc = LabelEncoder() y_ind = enc.fit_transform(y) classes_ = enc.classes_ if len(classes_) < 2: raise ValueError("This solver needs samples of at least 2 classes" " in the data, but the data contains only one" " class: %r" % classes_[0]) class_weight_ = compute_class_weight(class_weight, classes_, y) else: class_weight_ = np.empty(0, dtype=np.float64) y_ind = y liblinear.set_verbosity_wrap(verbose) rnd = check_random_state(random_state) if verbose: print('[LibLinear]', end='') # LinearSVC breaks when intercept_scaling is <= 0 bias = -1.0 if fit_intercept: if intercept_scaling <= 0: raise ValueError("Intercept scaling is %r but needs to be greater than 0." " To disable fitting an intercept," " set fit_intercept=False." % intercept_scaling) else: bias = intercept_scaling libsvm.set_verbosity_wrap(verbose) libsvm_sparse.set_verbosity_wrap(verbose) liblinear.set_verbosity_wrap(verbose) # LibLinear wants targets as doubles, even for classification y_ind = np.asarray(y_ind, dtype=np.float64).ravel() if sample_weight is None: sample_weight = np.ones(X.shape[0]) else: sample_weight = np.array(sample_weight, dtype=np.float64, order='C') check_consistent_length(sample_weight, X) solver_type = _get_liblinear_solver_type(multi_class, penalty, loss, dual) raw_coef_, n_iter_ = liblinear.train_wrap( X, y_ind, sp.isspmatrix(X), solver_type, tol, bias, C, class_weight_, max_iter, rnd.randint(np.iinfo('i').max), epsilon, sample_weight) # Regarding rnd.randint(..) in the above signature: # seed for srand in range [0..INT_MAX); due to limitations in Numpy # on 32-bit platforms, we can't get to the UINT_MAX limit that # srand supports n_iter_ = max(n_iter_) if n_iter_ >= max_iter and verbose > 0: warnings.warn("Liblinear failed to converge, increase " "the number of iterations.", ConvergenceWarning) if fit_intercept: coef_ = raw_coef_[:, :-1] intercept_ = intercept_scaling * raw_coef_[:, -1] else: coef_ = raw_coef_ intercept_ = 0. return coef_, intercept_, n_iter_