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This documentation is for scikit-learn version 0.15-gitOther versions

If you use the software, please consider citing scikit-learn.


This is the class and function reference of scikit-learn. Please refer to the full user guide for further details, as the class and function raw specifications may not be enough to give full guidelines on their uses.

sklearn.base: Base classes and utility functions

Base classes for all estimators.

Base classes

base.BaseEstimator Base class for all estimators in scikit-learn
base.ClassifierMixin Mixin class for all classifiers in scikit-learn.
base.ClusterMixin Mixin class for all cluster estimators in scikit-learn.
base.RegressorMixin Mixin class for all regression estimators in scikit-learn.
base.TransformerMixin Mixin class for all transformers in scikit-learn.


base.clone(estimator[, safe]) Constructs a new estimator with the same parameters.

sklearn.cluster: Clustering

The sklearn.cluster module gathers popular unsupervised clustering algorithms.

User guide: See the Clustering section for further details.


cluster.AffinityPropagation([damping, ...]) Perform Affinity Propagation Clustering of data.
cluster.AgglomerativeClustering([...]) Agglomerative Clustering
cluster.DBSCAN([eps, min_samples, metric, ...]) Perform DBSCAN clustering from vector array or distance matrix.
cluster.FeatureAgglomeration([n_clusters, ...])
cluster.KMeans([n_clusters, init, n_init, ...]) K-Means clustering
cluster.MiniBatchKMeans([n_clusters, init, ...]) Mini-Batch K-Means clustering
cluster.MeanShift([bandwidth, seeds, ...]) Mean shift clustering using a flat kernel.
cluster.SpectralClustering([n_clusters, ...]) Apply clustering to a projection to the normalized laplacian.
cluster.Ward([n_clusters, memory, ...]) Ward hierarchical clustering: constructs a tree and cuts it.


cluster.estimate_bandwidth(X[, quantile, ...]) Estimate the bandwidth to use with the mean-shift algorithm.
cluster.k_means(X, n_clusters[, init, ...]) K-means clustering algorithm.
cluster.ward_tree(X[, connectivity, ...]) Ward clustering based on a Feature matrix.
cluster.affinity_propagation(S[, ...]) Perform Affinity Propagation Clustering of data
cluster.dbscan(X[, eps, min_samples, ...]) Perform DBSCAN clustering from vector array or distance matrix.
cluster.mean_shift(X[, bandwidth, seeds, ...]) Perform mean shift clustering of data using a flat kernel.
cluster.spectral_clustering(affinity[, ...]) Apply clustering to a projection to the normalized laplacian.

sklearn.cluster.bicluster: Biclustering

User guide: See the Biclustering section for further details.


SpectralBiclustering([n_clusters, method, ...]) Spectral biclustering (Kluger, 2003).
SpectralCoclustering([n_clusters, ...]) Spectral Co-Clustering algorithm (Dhillon, 2001).

sklearn.covariance: Covariance Estimators

The sklearn.covariance module includes methods and algorithms to robustly estimate the covariance of features given a set of points. The precision matrix defined as the inverse of the covariance is also estimated. Covariance estimation is closely related to the theory of Gaussian Graphical Models.

User guide: See the Covariance estimation section for further details.

covariance.EmpiricalCovariance([...]) Maximum likelihood covariance estimator
covariance.EllipticEnvelope([...]) An object for detecting outliers in a Gaussian distributed dataset.
covariance.GraphLasso([alpha, mode, tol, ...]) Sparse inverse covariance estimation with an l1-penalized estimator.
covariance.GraphLassoCV([alphas, ...]) Sparse inverse covariance w/ cross-validated choice of the l1 penalty
covariance.LedoitWolf([store_precision, ...]) LedoitWolf Estimator
covariance.MinCovDet([store_precision, ...]) Minimum Covariance Determinant (MCD): robust estimator of covariance.
covariance.OAS([store_precision, ...]) Oracle Approximating Shrinkage Estimator
covariance.ShrunkCovariance([...]) Covariance estimator with shrinkage
covariance.empirical_covariance(X[, ...]) Computes the Maximum likelihood covariance estimator
covariance.ledoit_wolf(X[, assume_centered, ...]) Estimates the shrunk Ledoit-Wolf covariance matrix.
covariance.shrunk_covariance(emp_cov[, ...]) Calculates a covariance matrix shrunk on the diagonal
covariance.oas(X[, assume_centered]) Estimate covariance with the Oracle Approximating Shrinkage algorithm.
covariance.graph_lasso(emp_cov, alpha[, ...]) l1-penalized covariance estimator

sklearn.cross_validation: Cross Validation

The sklearn.cross_validation module includes utilities for cross- validation and performance evaluation.

User guide: See the Cross-validation: evaluating estimator performance section for further details.

cross_validation.KFold(n[, n_folds, ...]) K-Folds cross validation iterator.
cross_validation.LeaveOneLabelOut(labels[, ...]) Leave-One-Label_Out cross-validation iterator
cross_validation.LeaveOneOut(n[, indices]) Leave-One-Out cross validation iterator.
cross_validation.LeavePLabelOut(labels, p[, ...]) Leave-P-Label_Out cross-validation iterator
cross_validation.LeavePOut(n, p[, indices]) Leave-P-Out cross validation iterator
cross_validation.StratifiedKFold(y[, ...]) Stratified K-Folds cross validation iterator
cross_validation.ShuffleSplit(n[, n_iter, ...]) Random permutation cross-validation iterator.
cross_validation.StratifiedShuffleSplit(y[, ...]) Stratified ShuffleSplit cross validation iterator
cross_validation.train_test_split(*arrays, ...) Split arrays or matrices into random train and test subsets
cross_validation.cross_val_score(estimator, X) Evaluate a score by cross-validation
cross_validation.permutation_test_score(...) Evaluate the significance of a cross-validated score with permutations
cross_validation.check_cv(cv[, X, y, classifier]) Input checker utility for building a CV in a user friendly way.

sklearn.datasets: Datasets

The sklearn.datasets module includes utilities to load datasets, including methods to load and fetch popular reference datasets. It also features some artificial data generators.

User guide: See the Dataset loading utilities section for further details.


datasets.fetch_20newsgroups([data_home, ...]) Load the filenames and data from the 20 newsgroups dataset.
datasets.fetch_20newsgroups_vectorized([...]) Load the 20 newsgroups dataset and transform it into tf-idf vectors.
datasets.load_boston() Load and return the boston house-prices dataset (regression).
datasets.load_diabetes() Load and return the diabetes dataset (regression).
datasets.load_digits([n_class]) Load and return the digits dataset (classification).
datasets.load_files(container_path[, ...]) Load text files with categories as subfolder names.
datasets.load_iris() Load and return the iris dataset (classification).
datasets.load_lfw_pairs([download_if_missing]) Alias for fetch_lfw_pairs(download_if_missing=False)
datasets.fetch_lfw_pairs([subset, ...]) Loader for the Labeled Faces in the Wild (LFW) pairs dataset
datasets.load_lfw_people([download_if_missing]) Alias for fetch_lfw_people(download_if_missing=False)
datasets.fetch_lfw_people([data_home, ...]) Loader for the Labeled Faces in the Wild (LFW) people dataset
datasets.load_linnerud() Load and return the linnerud dataset (multivariate regression).
datasets.fetch_mldata(dataname[, ...]) Fetch an data set
datasets.fetch_olivetti_faces([data_home, ...]) Loader for the Olivetti faces data-set from AT&T.
datasets.fetch_california_housing([...]) Loader for the California housing dataset from StatLib.
datasets.fetch_covtype([data_home, ...]) Load the covertype dataset, downloading it if necessary.
datasets.load_mlcomp(name_or_id[, set_, ...]) Load a datasets as downloaded from
datasets.load_sample_image(image_name) Load the numpy array of a single sample image
datasets.load_sample_images() Load sample images for image manipulation.
datasets.load_svmlight_file(f[, n_features, ...]) Load datasets in the svmlight / libsvm format into sparse CSR matrix
datasets.dump_svmlight_file(X, y, f[, ...]) Dump the dataset in svmlight / libsvm file format.

Samples generator

datasets.make_blobs([n_samples, n_features, ...]) Generate isotropic Gaussian blobs for clustering.
datasets.make_classification([n_samples, ...]) Generate a random n-class classification problem.
datasets.make_circles([n_samples, shuffle, ...]) Make a large circle containing a smaller circle in 2d.
datasets.make_friedman1([n_samples, ...]) Generate the “Friedman #1” regression problem
datasets.make_friedman2([n_samples, noise, ...]) Generate the “Friedman #2” regression problem
datasets.make_friedman3([n_samples, noise, ...]) Generate the “Friedman #3” regression problem
datasets.make_gaussian_quantiles([mean, ...]) Generate isotropic Gaussian and label samples by quantile
datasets.make_hastie_10_2([n_samples, ...]) Generates data for binary classification used in Hastie et al.
datasets.make_low_rank_matrix([n_samples, ...]) Generate a mostly low rank matrix with bell-shaped singular values
datasets.make_moons([n_samples, shuffle, ...]) Make two interleaving half circles
datasets.make_multilabel_classification([...]) Generate a random multilabel classification problem.
datasets.make_regression([n_samples, ...]) Generate a random regression problem.
datasets.make_s_curve([n_samples, noise, ...]) Generate an S curve dataset.
datasets.make_sparse_coded_signal(n_samples, ...) Generate a signal as a sparse combination of dictionary elements.
datasets.make_sparse_spd_matrix([dim, ...]) Generate a sparse symmetric definite positive matrix.
datasets.make_sparse_uncorrelated([...]) Generate a random regression problem with sparse uncorrelated design
datasets.make_spd_matrix(n_dim[, random_state]) Generate a random symmetric, positive-definite matrix.
datasets.make_swiss_roll([n_samples, noise, ...]) Generate a swiss roll dataset.
datasets.make_biclusters(shape, n_clusters) Generate an array with constant block diagonal structure for biclustering.
datasets.make_checkerboard(shape, n_clusters) Generate an array with block checkerboard structure for biclustering.

sklearn.decomposition: Matrix Decomposition

The sklearn.decomposition module includes matrix decomposition algorithms, including among others PCA, NMF or ICA. Most of the algorithms of this module can be regarded as dimensionality reduction techniques.

User guide: See the Decomposing signals in components (matrix factorization problems) section for further details.

decomposition.PCA([n_components, copy, whiten]) Principal component analysis (PCA)
decomposition.ProjectedGradientNMF([...]) Non-Negative matrix factorization by Projected Gradient (NMF)
decomposition.RandomizedPCA([n_components, ...]) Principal component analysis (PCA) using randomized SVD
decomposition.KernelPCA([n_components, ...]) Kernel Principal component analysis (KPCA)
decomposition.FactorAnalysis([n_components, ...]) Factor Analysis (FA)
decomposition.FastICA([n_components, ...]) FastICA: a fast algorithm for Independent Component Analysis.
decomposition.TruncatedSVD([n_components, ...]) Dimensionality reduction using truncated SVD (aka LSA).
decomposition.NMF([n_components, init, ...]) Non-Negative matrix factorization by Projected Gradient (NMF)
decomposition.SparsePCA([n_components, ...]) Sparse Principal Components Analysis (SparsePCA)
decomposition.MiniBatchSparsePCA([...]) Mini-batch Sparse Principal Components Analysis
decomposition.SparseCoder(dictionary[, ...]) Sparse coding
decomposition.DictionaryLearning([...]) Dictionary learning
decomposition.MiniBatchDictionaryLearning([...]) Mini-batch dictionary learning
decomposition.fastica(X[, n_components, ...]) Perform Fast Independent Component Analysis.
decomposition.dict_learning(X, n_components, ...) Solves a dictionary learning matrix factorization problem.
decomposition.dict_learning_online(X[, ...]) Solves a dictionary learning matrix factorization problem online.
decomposition.sparse_encode(X, dictionary[, ...]) Sparse coding

sklearn.dummy: Dummy estimators

User guide: See the Model evaluation: quantifying the quality of predictions section for further details.

dummy.DummyClassifier([strategy, ...]) DummyClassifier is a classifier that makes predictions using simple rules.
dummy.DummyRegressor([strategy, constant]) DummyRegressor is a regressor that makes predictions using simple rules.

sklearn.ensemble: Ensemble Methods

The sklearn.ensemble module includes ensemble-based methods for classification and regression.

User guide: See the Ensemble methods section for further details.

ensemble.AdaBoostClassifier([...]) An AdaBoost classifier.
ensemble.AdaBoostRegressor([base_estimator, ...]) An AdaBoost regressor.
ensemble.BaggingClassifier([base_estimator, ...]) A Bagging classifier.
ensemble.BaggingRegressor([base_estimator, ...]) A Bagging regressor.
ensemble.ExtraTreesClassifier([...]) An extra-trees classifier.
ensemble.ExtraTreesRegressor([n_estimators, ...]) An extra-trees regressor.
ensemble.GradientBoostingClassifier([loss, ...]) Gradient Boosting for classification.
ensemble.GradientBoostingRegressor([loss, ...]) Gradient Boosting for regression.
ensemble.RandomForestClassifier([...]) A random forest classifier.
ensemble.RandomTreesEmbedding([...]) An ensemble of totally random trees.
ensemble.RandomForestRegressor([...]) A random forest regressor.

partial dependence

Partial dependence plots for tree ensembles.

ensemble.partial_dependence.partial_dependence(...) Partial dependence of target_variables.
ensemble.partial_dependence.plot_partial_dependence(...) Partial dependence plots for features.

sklearn.feature_extraction: Feature Extraction

The sklearn.feature_extraction module deals with feature extraction from raw data. It currently includes methods to extract features from text and images.

User guide: See the Feature extraction section for further details.

feature_extraction.DictVectorizer([dtype, ...]) Transforms lists of feature-value mappings to vectors.
feature_extraction.FeatureHasher([...]) Implements feature hashing, aka the hashing trick.

From images

The sklearn.feature_extraction.image submodule gathers utilities to extract features from images.

feature_extraction.image.img_to_graph(img[, ...]) Graph of the pixel-to-pixel gradient connections
feature_extraction.image.grid_to_graph(n_x, n_y) Graph of the pixel-to-pixel connections
feature_extraction.image.extract_patches_2d(...) Reshape a 2D image into a collection of patches
feature_extraction.image.reconstruct_from_patches_2d(...) Reconstruct the image from all of its patches.
feature_extraction.image.PatchExtractor([...]) Extracts patches from a collection of images

From text

The sklearn.feature_extraction.text submodule gathers utilities to build feature vectors from text documents.

feature_extraction.text.CountVectorizer([...]) Convert a collection of text documents to a matrix of token counts
feature_extraction.text.HashingVectorizer([...]) Convert a collection of text documents to a matrix of token occurrences
feature_extraction.text.TfidfTransformer([...]) Transform a count matrix to a normalized tf or tf-idf representation
feature_extraction.text.TfidfVectorizer([...]) Convert a collection of raw documents to a matrix of TF-IDF features.

sklearn.feature_selection: Feature Selection

The sklearn.feature_selection module implements feature selection algorithms. It currently includes univariate filter selection methods and the recursive feature elimination algorithm.

User guide: See the Feature selection section for further details.

feature_selection.GenericUnivariateSelect([...]) Univariate feature selector with configurable strategy.
feature_selection.SelectPercentile([...]) Select features according to a percentile of the highest scores.
feature_selection.SelectKBest([score_func, k]) Select features according to the k highest scores.
feature_selection.SelectFpr([score_func, alpha]) Filter: Select the pvalues below alpha based on a FPR test.
feature_selection.SelectFdr([score_func, alpha]) Filter: Select the p-values for an estimated false discovery rate
feature_selection.SelectFwe([score_func, alpha]) Filter: Select the p-values corresponding to Family-wise error rate
feature_selection.RFE(estimator[, ...]) Feature ranking with recursive feature elimination.
feature_selection.RFECV(estimator[, step, ...]) Feature ranking with recursive feature elimination and cross-validated selection of the best number of features.
feature_selection.VarianceThreshold([threshold]) Feature selector that removes all low-variance features.
feature_selection.chi2(X, y) Compute chi-squared statistic for each class/feature combination.
feature_selection.f_classif(X, y) Compute the Anova F-value for the provided sample
feature_selection.f_regression(X, y[, center]) Univariate linear regression tests

sklearn.gaussian_process: Gaussian Processes

The sklearn.gaussian_process module implements scalar Gaussian Process based predictions.

User guide: See the Gaussian Processes section for further details.

gaussian_process.GaussianProcess([regr, ...]) The Gaussian Process model class.
gaussian_process.correlation_models.absolute_exponential(...) Absolute exponential autocorrelation model.
gaussian_process.correlation_models.squared_exponential(...) Squared exponential correlation model (Radial Basis Function).
gaussian_process.correlation_models.generalized_exponential(...) Generalized exponential correlation model.
gaussian_process.correlation_models.pure_nugget(...) Spatial independence correlation model (pure nugget).
gaussian_process.correlation_models.cubic(...) Cubic correlation model:
gaussian_process.correlation_models.linear(...) Linear correlation model:
gaussian_process.regression_models.constant(x) Zero order polynomial (constant, p = 1) regression model.
gaussian_process.regression_models.linear(x) First order polynomial (linear, p = n+1) regression model.
gaussian_process.regression_models.quadratic(x) Second order polynomial (quadratic, p = n*(n-1)/2+n+1) regression model.

sklearn.isotonic: Isotonic regression

User guide: See the Isotonic regression section for further details.

isotonic.IsotonicRegression([y_min, y_max, ...]) Isotonic regression model.
isotonic.isotonic_regression(y[, ...]) Solve the isotonic regression model:
isotonic.check_increasing(x, y) Determine whether y is monotonically correlated with x.

sklearn.kernel_approximation Kernel Approximation

The sklearn.kernel_approximation module implements several approximate kernel feature maps base on Fourier transforms.

User guide: See the Kernel Approximation section for further details.

kernel_approximation.AdditiveChi2Sampler([...]) Approximate feature map for additive chi2 kernel.
kernel_approximation.Nystroem([kernel, ...]) Approximate a kernel map using a subset of the training data.
kernel_approximation.RBFSampler([gamma, ...]) Approximates feature map of an RBF kernel by Monte Carlo approximation of its Fourier transform.
kernel_approximation.SkewedChi2Sampler([...]) Approximates feature map of the “skewed chi-squared” kernel by Monte Carlo approximation of its Fourier transform.

sklearn.lda: Linear Discriminant Analysis

The sklearn.lda module implements Linear Discriminant Analysis (LDA).

User guide: See the Linear and quadratic discriminant analysis section for further details.

lda.LDA([n_components, priors]) Linear Discriminant Analysis (LDA)

sklearn.learning_curve Learning curve evaluation

Utilities to evaluate models with respect to a variable

learning_curve.learning_curve(estimator, X, y) Learning curve.
learning_curve.validation_curve(estimator, ...) Validation curve.

sklearn.linear_model: Generalized Linear Models

The sklearn.linear_model module implements generalized linear models. It includes Ridge regression, Bayesian Regression, Lasso and Elastic Net estimators computed with Least Angle Regression and coordinate descent. It also implements Stochastic Gradient Descent related algorithms.

User guide: See the Generalized Linear Models section for further details.

linear_model.ARDRegression([n_iter, tol, ...]) Bayesian ARD regression.
linear_model.BayesianRidge([n_iter, tol, ...]) Bayesian ridge regression
linear_model.ElasticNet([alpha, l1_ratio, ...]) Linear regression with combined L1 and L2 priors as regularizer.
linear_model.ElasticNetCV([l1_ratio, eps, ...]) Elastic Net model with iterative fitting along a regularization path
linear_model.Lars([fit_intercept, verbose, ...]) Least Angle Regression model a.k.a.
linear_model.LarsCV([fit_intercept, ...]) Cross-validated Least Angle Regression model
linear_model.Lasso([alpha, fit_intercept, ...]) Linear Model trained with L1 prior as regularizer (aka the Lasso)
linear_model.LassoCV([eps, n_alphas, ...]) Lasso linear model with iterative fitting along a regularization path
linear_model.LassoLars([alpha, ...]) Lasso model fit with Least Angle Regression a.k.a.
linear_model.LassoLarsCV([fit_intercept, ...]) Cross-validated Lasso, using the LARS algorithm
linear_model.LassoLarsIC([criterion, ...]) Lasso model fit with Lars using BIC or AIC for model selection
linear_model.LinearRegression([...]) Ordinary least squares Linear Regression.
linear_model.LogisticRegression([penalty, ...]) Logistic Regression (aka logit, MaxEnt) classifier.
linear_model.MultiTaskLasso([alpha, ...]) Multi-task Lasso model trained with L1/L2 mixed-norm as regularizer
linear_model.MultiTaskElasticNet([alpha, ...]) Multi-task ElasticNet model trained with L1/L2 mixed-norm as regularizer
linear_model.MultiTaskLassoCV([eps, ...]) Multi-task L1/L2 Lasso with built-in cross-validation.
linear_model.MultiTaskElasticNetCV([...]) Multi-task L1/L2 ElasticNet with built-in cross-validation.
linear_model.OrthogonalMatchingPursuit([...]) Orthogonal Mathching Pursuit model (OMP)
linear_model.OrthogonalMatchingPursuitCV([...]) Cross-validated Orthogonal Mathching Pursuit model (OMP)
linear_model.PassiveAggressiveClassifier([...]) Passive Aggressive Classifier
linear_model.PassiveAggressiveRegressor([C, ...]) Passive Aggressive Regressor
linear_model.Perceptron([penalty, alpha, ...]) Perceptron
linear_model.RandomizedLasso([alpha, ...]) Randomized Lasso.
linear_model.RandomizedLogisticRegression([...]) Randomized Logistic Regression
linear_model.RANSACRegressor([...]) RANSAC (RANdom SAmple Consensus) algorithm.
linear_model.Ridge([alpha, fit_intercept, ...]) Linear least squares with l2 regularization.
linear_model.RidgeClassifier([alpha, ...]) Classifier using Ridge regression.
linear_model.RidgeClassifierCV([alphas, ...]) Ridge classifier with built-in cross-validation.
linear_model.RidgeCV([alphas, ...]) Ridge regression with built-in cross-validation.
linear_model.SGDClassifier([loss, penalty, ...]) Linear classifiers (SVM, logistic regression, a.o.) with SGD training.
linear_model.SGDRegressor([loss, penalty, ...]) Linear model fitted by minimizing a regularized empirical loss with SGD
linear_model.lars_path(X, y[, Xy, Gram, ...]) Compute Least Angle Regression or Lasso path using LARS algorithm [1]
linear_model.lasso_path(X, y[, eps, ...]) Compute Lasso path with coordinate descent
linear_model.lasso_stability_path(X, y[, ...]) Stabiliy path based on randomized Lasso estimates
linear_model.orthogonal_mp(X, y[, ...]) Orthogonal Matching Pursuit (OMP)
linear_model.orthogonal_mp_gram(Gram, Xy[, ...]) Gram Orthogonal Matching Pursuit (OMP)

sklearn.manifold: Manifold Learning

The sklearn.manifold module implements data embedding techniques.

User guide: See the Manifold learning section for further details.

manifold.LocallyLinearEmbedding([...]) Locally Linear Embedding
manifold.Isomap([n_neighbors, n_components, ...]) Isomap Embedding
manifold.MDS([n_components, metric, n_init, ...]) Multidimensional scaling
manifold.SpectralEmbedding([n_components, ...]) Spectral embedding for non-linear dimensionality reduction.
manifold.TSNE([n_components, perplexity, ...]) t-distributed Stochastic Neighbor Embedding.
manifold.locally_linear_embedding(X, ...[, ...]) Perform a Locally Linear Embedding analysis on the data.
manifold.spectral_embedding(adjacency[, ...]) Project the sample on the first eigen vectors of the graph Laplacian.

sklearn.metrics: Metrics

See the Model evaluation: quantifying the quality of predictions section and the Pairwise metrics, Affinities and Kernels section of the user guide for further details.

The sklearn.metrics module includes score functions, performance metrics and pairwise metrics and distance computations.

Model Selection Interface

See the The scoring parameter: defining model evaluation rules section of the user guide for further details.

metrics.make_scorer(score_func[, ...]) Make a scorer from a performance metric or loss function.

Classification metrics

See the Classification metrics section of the user guide for further details.

metrics.accuracy_score(y_true, y_pred[, ...]) Accuracy classification score.
metrics.auc(x, y[, reorder]) Compute Area Under the Curve (AUC) using the trapezoidal rule
metrics.average_precision_score(y_true, y_score) Compute average precision (AP) from prediction scores
metrics.classification_report(y_true, y_pred) Build a text report showing the main classification metrics
metrics.confusion_matrix(y_true, y_pred[, ...]) Compute confusion matrix to evaluate the accuracy of a classification
metrics.f1_score(y_true, y_pred[, labels, ...]) Compute the F1 score, also known as balanced F-score or F-measure
metrics.fbeta_score(y_true, y_pred, beta[, ...]) Compute the F-beta score
metrics.hamming_loss(y_true, y_pred[, classes]) Compute the average Hamming loss.
metrics.hinge_loss(y_true, pred_decision[, ...]) Average hinge loss (non-regularized)
metrics.jaccard_similarity_score(y_true, y_pred) Jaccard similarity coefficient score
metrics.log_loss(y_true, y_pred[, eps, ...]) Log loss, aka logistic loss or cross-entropy loss.
metrics.matthews_corrcoef(y_true, y_pred) Compute the Matthews correlation coefficient (MCC) for binary classes
metrics.precision_recall_curve(y_true, ...) Compute precision-recall pairs for different probability thresholds
metrics.precision_recall_fscore_support(...) Compute precision, recall, F-measure and support for each class
metrics.precision_score(y_true, y_pred[, ...]) Compute the precision
metrics.recall_score(y_true, y_pred[, ...]) Compute the recall
metrics.roc_auc_score(y_true, y_score[, ...]) Compute Area Under the Curve (AUC) from prediction scores
metrics.roc_curve(y_true, y_score[, ...]) Compute Receiver operating characteristic (ROC)
metrics.zero_one_loss(y_true, y_pred[, ...]) Zero-one classification loss.

Regression metrics

See the Regression metrics section of the user guide for further details.

metrics.explained_variance_score(y_true, y_pred) Explained variance regression score function
metrics.mean_absolute_error(y_true, y_pred) Mean absolute error regression loss
metrics.mean_squared_error(y_true, y_pred[, ...]) Mean squared error regression loss
metrics.r2_score(y_true, y_pred[, sample_weight]) R^2 (coefficient of determination) regression score function.

Clustering metrics

See the Clustering performance evaluation section of the user guide for further details.

The sklearn.metrics.cluster submodule contains evaluation metrics for cluster analysis results. There are two forms of evaluation:

  • supervised, which uses a ground truth class values for each sample.
  • unsupervised, which does not and measures the ‘quality’ of the model itself.
metrics.adjusted_mutual_info_score(...) Adjusted Mutual Information between two clusterings
metrics.adjusted_rand_score(labels_true, ...) Rand index adjusted for chance
metrics.completeness_score(labels_true, ...) Completeness metric of a cluster labeling given a ground truth
metrics.homogeneity_completeness_v_measure(...) Compute the homogeneity and completeness and V-Measure scores at once
metrics.homogeneity_score(labels_true, ...) Homogeneity metric of a cluster labeling given a ground truth
metrics.mutual_info_score(labels_true, ...) Mutual Information between two clusterings
metrics.normalized_mutual_info_score(...) Normalized Mutual Information between two clusterings
metrics.silhouette_score(X, labels[, ...]) Compute the mean Silhouette Coefficient of all samples.
metrics.silhouette_samples(X, labels[, metric]) Compute the Silhouette Coefficient for each sample.
metrics.v_measure_score(labels_true, labels_pred) V-measure cluster labeling given a ground truth.

Biclustering metrics

See the Biclustering evaluation section of the user guide for further details.

metrics.consensus_score(a, b[, similarity]) The similarity of two sets of biclusters.

Pairwise metrics

The sklearn.metrics.pairwise submodule implements utilities to evaluate pairwise distances, paired distances or affinity of sets of samples.

This module contains both distance metrics and kernels. A brief summary is given on the two here.

Distance metrics are a function d(a, b) such that d(a, b) < d(a, c) if objects a and b are considered “more similar” to objects a and c. Two objects exactly alike would have a distance of zero. One of the most popular examples is Euclidean distance. To be a ‘true’ metric, it must obey the following four conditions:

1. d(a, b) >= 0, for all a and b
2. d(a, b) == 0, if and only if a = b, positive definiteness
3. d(a, b) == d(b, a), symmetry
4. d(a, c) <= d(a, b) + d(b, c), the triangle inequality

Kernels are measures of similarity, i.e. s(a, b) > s(a, c) if objects a and b are considered “more similar” to objects a and c. A kernel must also be positive semi-definite.

There are a number of ways to convert between a distance metric and a similarity measure, such as a kernel. Let D be the distance, and S be the kernel:

  1. S = np.exp(-D * gamma), where one heuristic for choosing gamma is 1 / num_features
  2. S = 1. / (D / np.max(D))
metrics.pairwise.additive_chi2_kernel(X[, Y]) Computes the additive chi-squared kernel between observations in X and Y
metrics.pairwise.chi2_kernel(X[, Y, gamma]) Computes the exponential chi-squared kernel X and Y.
metrics.pairwise.distance_metrics() Valid metrics for pairwise_distances.
metrics.pairwise.euclidean_distances(X[, Y, ...]) Considering the rows of X (and Y=X) as vectors, compute the distance matrix between each pair of vectors.
metrics.pairwise.kernel_metrics() Valid metrics for pairwise_kernels
metrics.pairwise.linear_kernel(X[, Y]) Compute the linear kernel between X and Y.
metrics.pairwise.manhattan_distances(X[, Y, ...]) Compute the L1 distances between the vectors in X and Y.
metrics.pairwise.pairwise_distances(X[, Y, ...]) Compute the distance matrix from a vector array X and optional Y.
metrics.pairwise.pairwise_kernels(X[, Y, ...]) Compute the kernel between arrays X and optional array Y.
metrics.pairwise.polynomial_kernel(X[, Y, ...]) Compute the polynomial kernel between X and Y:
metrics.pairwise.rbf_kernel(X[, Y, gamma]) Compute the rbf (gaussian) kernel between X and Y:
metrics.pairwise_distances(X[, Y, metric, ...]) Compute the distance matrix from a vector array X and optional Y.
metrics.pairwise_distances_argmin(X, Y[, ...]) Compute minimum distances between one point and a set of points.
metrics.pairwise_distances_argmin_min(X, Y) Compute minimum distances between one point and a set of points.

sklearn.mixture: Gaussian Mixture Models

The sklearn.mixture module implements mixture modeling algorithms.

User guide: See the Gaussian mixture models section for further details.

mixture.GMM([n_components, covariance_type, ...]) Gaussian Mixture Model
mixture.DPGMM([n_components, ...]) Variational Inference for the Infinite Gaussian Mixture Model.
mixture.VBGMM([n_components, ...]) Variational Inference for the Gaussian Mixture Model

sklearn.multiclass: Multiclass and multilabel classification

Multiclass and multilabel classification strategies

This module implements multiclass learning algorithms:
  • one-vs-the-rest / one-vs-all
  • one-vs-one
  • error correcting output codes

The estimators provided in this module are meta-estimators: they require a base estimator to be provided in their constructor. For example, it is possible to use these estimators to turn a binary classifier or a regressor into a multiclass classifier. It is also possible to use these estimators with multiclass estimators in the hope that their accuracy or runtime performance improves.

All classifiers in scikit-learn implement multiclass classification; you only need to use this module if you want to experiment with custom multiclass strategies.

The one-vs-the-rest meta-classifier also implements a predict_proba method, so long as such a method is implemented by the base classifier. This method returns probabilities of class membership in both the single label and multilabel case. Note that in the multilabel case, probabilities are the marginal probability that a given sample falls in the given class. As such, in the multilabel case the sum of these probabilities over all possible labels for a given sample will not sum to unity, as they do in the single label case.

User guide: See the Multiclass and multilabel algorithms section for further details.

multiclass.OneVsRestClassifier(estimator[, ...]) One-vs-the-rest (OvR) multiclass/multilabel strategy
multiclass.OneVsOneClassifier(estimator[, ...]) One-vs-one multiclass strategy
multiclass.OutputCodeClassifier(estimator[, ...]) (Error-Correcting) Output-Code multiclass strategy
multiclass.fit_ovr(estimator, X, y[, n_jobs]) Fit a one-vs-the-rest strategy.
multiclass.predict_ovr(estimators, ...) Make predictions using the one-vs-the-rest strategy.
multiclass.fit_ovo(estimator, X, y[, n_jobs]) Fit a one-vs-one strategy.
multiclass.predict_ovo(estimators, classes, X) Make predictions using the one-vs-one strategy.
multiclass.fit_ecoc(estimator, X, y[, ...]) Fit an error-correcting output-code strategy.
multiclass.predict_ecoc(estimators, classes, ...) Make predictions using the error-correcting output-code strategy.

sklearn.naive_bayes: Naive Bayes

The sklearn.naive_bayes module implements Naive Bayes algorithms. These are supervised learning methods based on applying Bayes’ theorem with strong (naive) feature independence assumptions.

User guide: See the Naive Bayes section for further details.

naive_bayes.GaussianNB Gaussian Naive Bayes (GaussianNB)
naive_bayes.MultinomialNB([alpha, ...]) Naive Bayes classifier for multinomial models
naive_bayes.BernoulliNB([alpha, binarize, ...]) Naive Bayes classifier for multivariate Bernoulli models.

sklearn.neighbors: Nearest Neighbors

The sklearn.neighbors module implements the k-nearest neighbors algorithm.

User guide: See the Nearest Neighbors section for further details.

neighbors.NearestNeighbors([n_neighbors, ...]) Unsupervised learner for implementing neighbor searches.
neighbors.KNeighborsClassifier([...]) Classifier implementing the k-nearest neighbors vote.
neighbors.RadiusNeighborsClassifier([...]) Classifier implementing a vote among neighbors within a given radius
neighbors.KNeighborsRegressor([n_neighbors, ...]) Regression based on k-nearest neighbors.
neighbors.RadiusNeighborsRegressor([radius, ...]) Regression based on neighbors within a fixed radius.
neighbors.NearestCentroid([metric, ...]) Nearest centroid classifier.
neighbors.BallTree BallTree for fast generalized N-point problems
neighbors.KDTree KDTree for fast generalized N-point problems
neighbors.DistanceMetric DistanceMetric class
neighbors.KernelDensity([bandwidth, ...]) Kernel Density Estimation
neighbors.kneighbors_graph(X, n_neighbors[, ...]) Computes the (weighted) graph of k-Neighbors for points in X
neighbors.radius_neighbors_graph(X, radius) Computes the (weighted) graph of Neighbors for points in X

sklearn.neural_network: Neural network models

The sklearn.neural_network module includes models based on neural networks.

User guide: See the Neural network models (unsupervised) section for further details.

neural_network.BernoulliRBM([n_components, ...]) Bernoulli Restricted Boltzmann Machine (RBM).

sklearn.cross_decomposition: Cross decomposition

User guide: See the Cross decomposition section for further details.

cross_decomposition.PLSRegression([...]) PLS regression
cross_decomposition.PLSCanonical([...]) PLSCanonical implements the 2 blocks canonical PLS of the original Wold algorithm [Tenenhaus 1998] p.204, referred as PLS-C2A in [Wegelin 2000].
cross_decomposition.CCA([n_components, ...]) CCA Canonical Correlation Analysis.
cross_decomposition.PLSSVD([n_components, ...]) Partial Least Square SVD

sklearn.pipeline: Pipeline

The sklearn.pipeline module implements utilities to build a composite estimator, as a chain of transforms and estimators.

pipeline.Pipeline(steps) Pipeline of transforms with a final estimator.
pipeline.FeatureUnion(transformer_list[, ...]) Concatenates results of multiple transformer objects.
pipeline.make_pipeline(*steps) Construct a Pipeline from the given estimators.
pipeline.make_union(*transformers) Construct a FeatureUnion from the given transformers.

sklearn.preprocessing: Preprocessing and Normalization

The sklearn.preprocessing module includes scaling, centering, normalization, binarization and imputation methods.

User guide: See the Preprocessing data section for further details.

preprocessing.Binarizer([threshold, copy]) Binarize data (set feature values to 0 or 1) according to a threshold
preprocessing.Imputer([missing_values, ...]) Imputation transformer for completing missing values.
preprocessing.KernelCenterer Center a kernel matrix
preprocessing.LabelBinarizer([neg_label, ...]) Binarize labels in a one-vs-all fashion
preprocessing.LabelEncoder Encode labels with value between 0 and n_classes-1.
preprocessing.MultiLabelBinarizer([classes, ...]) Transform between iterable of iterables and a multilabel format
preprocessing.MinMaxScaler([feature_range, copy]) Standardizes features by scaling each feature to a given range.
preprocessing.Normalizer([norm, copy]) Normalize samples individually to unit norm
preprocessing.OneHotEncoder([n_values, ...]) Encode categorical integer features using a one-hot aka one-of-K scheme.
preprocessing.StandardScaler([copy, ...]) Standardize features by removing the mean and scaling to unit variance
preprocessing.PolynomialFeatures([degree, ...]) Generate polynomial and interaction features.
preprocessing.add_dummy_feature(X[, value]) Augment dataset with an additional dummy feature.
preprocessing.binarize(X[, threshold, copy]) Boolean thresholding of array-like or scipy.sparse matrix
preprocessing.label_binarize(y, classes[, ...]) Binarize labels in a one-vs-all fashion
preprocessing.normalize(X[, norm, axis, copy]) Normalize a dataset along any axis
preprocessing.scale(X[, axis, with_mean, ...]) Standardize a dataset along any axis

sklearn.qda: Quadratic Discriminant Analysis

Quadratic Discriminant Analysis

User guide: See the Linear and quadratic discriminant analysis section for further details.

qda.QDA([priors, reg_param]) Quadratic Discriminant Analysis (QDA)

sklearn.random_projection: Random projection

Random Projection transformers

Random Projections are a simple and computationally efficient way to reduce the dimensionality of the data by trading a controlled amount of accuracy (as additional variance) for faster processing times and smaller model sizes.

The dimensions and distribution of Random Projections matrices are controlled so as to preserve the pairwise distances between any two samples of the dataset.

The main theoretical result behind the efficiency of random projection is the Johnson-Lindenstrauss lemma (quoting Wikipedia):

In mathematics, the Johnson-Lindenstrauss lemma is a result concerning low-distortion embeddings of points from high-dimensional into low-dimensional Euclidean space. The lemma states that a small set of points in a high-dimensional space can be embedded into a space of much lower dimension in such a way that distances between the points are nearly preserved. The map used for the embedding is at least Lipschitz, and can even be taken to be an orthogonal projection.

User guide: See the Random Projection section for further details.

random_projection.GaussianRandomProjection([...]) Reduce dimensionality through Gaussian random projection
random_projection.SparseRandomProjection([...]) Reduce dimensionality through sparse random projection
random_projection.johnson_lindenstrauss_min_dim(...) Find a ‘safe’ number of components to randomly project to

sklearn.semi_supervised Semi-Supervised Learning

The sklearn.semi_supervised module implements semi-supervised learning algorithms. These algorithms utilized small amounts of labeled data and large amounts of unlabeled data for classification tasks. This module includes Label Propagation.

User guide: See the Semi-Supervised section for further details.

semi_supervised.LabelPropagation([kernel, ...]) Label Propagation classifier
semi_supervised.LabelSpreading([kernel, ...]) LabelSpreading model for semi-supervised learning

sklearn.svm: Support Vector Machines

The sklearn.svm module includes Support Vector Machine algorithms.

User guide: See the Support Vector Machines section for further details.


svm.SVC([C, kernel, degree, gamma, coef0, ...]) C-Support Vector Classification.
svm.LinearSVC([penalty, loss, dual, tol, C, ...]) Linear Support Vector Classification.
svm.NuSVC([nu, kernel, degree, gamma, ...]) Nu-Support Vector Classification.
svm.SVR([kernel, degree, gamma, coef0, tol, ...]) epsilon-Support Vector Regression.
svm.NuSVR([nu, C, kernel, degree, gamma, ...]) Nu Support Vector Regression.
svm.OneClassSVM([kernel, degree, gamma, ...]) Unsupervised Outliers Detection.
svm.l1_min_c(X, y[, loss, fit_intercept, ...]) Return the lowest bound for C such that for C in (l1_min_C, infinity) the model is guaranteed not to be empty.

Low-level methods Train the model using libsvm (low-level method)
svm.libsvm.decision_function Predict margin (libsvm name for this is predict_values)
svm.libsvm.predict Predict target values of X given a model (low-level method)
svm.libsvm.predict_proba Predict probabilities
svm.libsvm.cross_validation Binding of the cross-validation routine (low-level routine)

sklearn.tree: Decision Trees

The sklearn.tree module includes decision tree-based models for classification and regression.

User guide: See the Decision Trees section for further details.

tree.DecisionTreeClassifier([criterion, ...]) A decision tree classifier.
tree.DecisionTreeRegressor([criterion, ...]) A decision tree regressor.
tree.ExtraTreeClassifier([criterion, ...]) An extremely randomized tree classifier.
tree.ExtraTreeRegressor([criterion, ...]) An extremely randomized tree regressor.
tree.export_graphviz(decision_tree[, ...]) Export a decision tree in DOT format.

sklearn.utils: Utilities

The sklearn.utils module includes various utilities.

Developer guide: See the Utilities for Developers page for further details.

utils.check_random_state(seed) Turn seed into a np.random.RandomState instance
utils.resample(*arrays, **options) Resample arrays or sparse matrices in a consistent way
utils.shuffle(*arrays, **options) Shuffle arrays or sparse matrices in a consistent way