## File: plot_label_propagation_digits_active_learning.py

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scikit-learn 0.18-5
 `123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899` ``````""" ======================================== Label Propagation digits active learning ======================================== Demonstrates an active learning technique to learn handwritten digits using label propagation. We start by training a label propagation model with only 10 labeled points, then we select the top five most uncertain points to label. Next, we train with 15 labeled points (original 10 + 5 new ones). We repeat this process four times to have a model trained with 30 labeled examples. A plot will appear showing the top 5 most uncertain digits for each iteration of training. These may or may not contain mistakes, but we will train the next model with their true labels. """ print(__doc__) # Authors: Clay Woolam # License: BSD import numpy as np import matplotlib.pyplot as plt from scipy import stats from sklearn import datasets from sklearn.semi_supervised import label_propagation from sklearn.metrics import classification_report, confusion_matrix digits = datasets.load_digits() rng = np.random.RandomState(0) indices = np.arange(len(digits.data)) rng.shuffle(indices) X = digits.data[indices[:330]] y = digits.target[indices[:330]] images = digits.images[indices[:330]] n_total_samples = len(y) n_labeled_points = 10 unlabeled_indices = np.arange(n_total_samples)[n_labeled_points:] f = plt.figure() for i in range(5): y_train = np.copy(y) y_train[unlabeled_indices] = -1 lp_model = label_propagation.LabelSpreading(gamma=0.25, max_iter=5) lp_model.fit(X, y_train) predicted_labels = lp_model.transduction_[unlabeled_indices] true_labels = y[unlabeled_indices] cm = confusion_matrix(true_labels, predicted_labels, labels=lp_model.classes_) print('Iteration %i %s' % (i, 70 * '_')) print("Label Spreading model: %d labeled & %d unlabeled (%d total)" % (n_labeled_points, n_total_samples - n_labeled_points, n_total_samples)) print(classification_report(true_labels, predicted_labels)) print("Confusion matrix") print(cm) # compute the entropies of transduced label distributions pred_entropies = stats.distributions.entropy( lp_model.label_distributions_.T) # select five digit examples that the classifier is most uncertain about uncertainty_index = uncertainty_index = np.argsort(pred_entropies)[-5:] # keep track of indices that we get labels for delete_indices = np.array([]) f.text(.05, (1 - (i + 1) * .183), "model %d\n\nfit with\n%d labels" % ((i + 1), i * 5 + 10), size=10) for index, image_index in enumerate(uncertainty_index): image = images[image_index] sub = f.add_subplot(5, 5, index + 1 + (5 * i)) sub.imshow(image, cmap=plt.cm.gray_r) sub.set_title('predict: %i\ntrue: %i' % ( lp_model.transduction_[image_index], y[image_index]), size=10) sub.axis('off') # labeling 5 points, remote from labeled set delete_index, = np.where(unlabeled_indices == image_index) delete_indices = np.concatenate((delete_indices, delete_index)) unlabeled_indices = np.delete(unlabeled_indices, delete_indices) n_labeled_points += 5 f.suptitle("Active learning with Label Propagation.\nRows show 5 most " "uncertain labels to learn with the next model.") plt.subplots_adjust(0.12, 0.03, 0.9, 0.8, 0.2, 0.45) plt.show() ``````