import numpy as np import matplotlib.pyplot as plt from sklearn.naive_bayes import GaussianNB from sklearn.svm import SVC from sklearn.datasets import load_digits from sklearn.model_selection import learning_curve from sklearn.model_selection import ShuffleSplit def plot_learning_curve(estimator, title, X, y, ylim=None, cv=None, n_jobs=1, train_sizes=np.linspace(.1, 1.0, 5)): """ Generate a simple plot of the test and training learning curve. Parameters ---------- estimator : object type that implements the "fit" and "predict" methods An object of that type which is cloned for each validation. title : string Title for the chart. X : array-like, shape (n_samples, n_features) Training vector, where n_samples is the number of samples and n_features is the number of features. y : array-like, shape (n_samples) or (n_samples, n_features), optional Target relative to X for classification or regression; None for unsupervised learning. ylim : tuple, shape (ymin, ymax), optional Defines minimum and maximum yvalues plotted. cv : int, cross-validation generator or an iterable, optional Determines the cross-validation splitting strategy. Possible inputs for cv are: - None, to use the default 3-fold cross-validation, - integer, to specify the number of folds. - An object to be used as a cross-validation generator. - An iterable yielding train/test splits. For integer/None inputs, if ``y`` is binary or multiclass, :class:`StratifiedKFold` used. If the estimator is not a classifier or if ``y`` is neither binary nor multiclass, :class:`KFold` is used. Refer :ref:`User Guide <cross_validation>` for the various cross-validators that can be used here. n_jobs : integer, optional Number of jobs to run in parallel (default 1). """ plt.figure() plt.title(title) if ylim is not None: plt.ylim(*ylim) plt.xlabel("Training examples") plt.ylabel("Score") train_sizes, train_scores, test_scores = learning_curve( estimator, X, y, cv=cv, n_jobs=n_jobs, train_sizes=train_sizes) train_scores_mean = np.mean(train_scores, axis=1) train_scores_std = np.std(train_scores, axis=1) test_scores_mean = np.mean(test_scores, axis=1) test_scores_std = np.std(test_scores, axis=1) plt.grid() plt.fill_between(train_sizes, train_scores_mean - train_scores_std, train_scores_mean + train_scores_std, alpha=0.1, color="r") plt.fill_between(train_sizes, test_scores_mean - test_scores_std, test_scores_mean + test_scores_std, alpha=0.1, color="g") plt.plot(train_sizes, train_scores_mean, 'o-', color="r", label="Training score") plt.plot(train_sizes, test_scores_mean, 'o-', color="g", label="Cross-validation score") plt.legend(loc="best") return plt digits = load_digits() X, y = digits.data, digits.target title = "Learning Curves (Naive Bayes)" # Cross validation with 100 iterations to get smoother mean test and train # score curves, each time with 20% data randomly selected as a validation set. cv = ShuffleSplit(n_splits=100, test_size=0.2, random_state=0) estimator = GaussianNB() plot_learning_curve(estimator, title, X, y, ylim=(0.7, 1.01), cv=cv, n_jobs=4) title = "Learning Curves (SVM, RBF kernel, $gamma=0.001$)" # SVC is more expensive so we do a lower number of CV iterations: cv = ShuffleSplit(n_splits=10, test_size=0.2, random_state=0) estimator = SVC(gamma=0.001) plot_learning_curve(estimator, title, X, y, (0.7, 1.01), cv=cv, n_jobs=4) plt.show()