solution for exercise 04

Author: ogrisel

solutions/exercise_04_face_recognition.py

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+"""Face recognition using PCA (eigenfaces) and SVM"""
+# License: Simplified BSD
+
+import os
+from gzip import GzipFile
+
+import sys
+import numpy as np
+import pylab as pl
+
+from scikits.learn.grid_search import GridSearchCV
+from scikits.learn.metrics import classification_report
+from scikits.learn.metrics import confusion_matrix
+from scikits.learn.pca import RandomizedPCA
+from scikits.learn.svm import SVC
+
+# Load dataset in memory
+folder_name = sys.argv[1]
+faces_filename = os.path.join(folder_name, "faces.npy.gz")
+filenames_filename = os.path.join(folder_name, "face_filenames.txt")
+
+faces = np.load(GzipFile(faces_filename))
+face_filenames = [l.strip() for l in file(filenames_filename).readlines()]
+
+# normalize each picture by centering brightness
+faces -= faces.mean(axis=1)[:, np.newaxis]
+
+
+# Index category names into integers suitable for scikit-learn
+#
+# Here we do a little dance to convert file names in integer indices
+# (class indices in machine learning talk) that are suitable to be used
+# as a target for training a classifier. Note the use of an array with
+# unique entries to store the relation between class index and name,
+# often called a 'Look Up Table' (LUT).
+# Also, note the use of 'searchsorted' to convert an array in a set of
+# integers given a second array to use as a LUT.
+person_names = np.array([f.rsplit('_', 1)[0] for f in face_filenames])
+
+# A unique integer per category
+target_names = np.unique(person_names)
+
+# Turn the person_names in their corresponding integer label
+target = np.searchsorted(target_names, person_names)
+
+# Subsample the dataset to restrict to the most frequent person_names
+selected_target = np.argsort(np.bincount(target))[-5:]
+most_frequent_mask = np.array([item in selected_target for item in target])
+
+X = faces[most_frequent_mask]
+y = target[most_frequent_mask]
+
+n_samples, n_features = X.shape
+
+print "Dataset size:"
+print "n_samples: %d" % n_samples
+print "n_features: %d" % n_features
+
+# Split the dataset into a training and test set
+
+split = n_samples * 3 / 4
+
+X_train, X_test = X[:split], X[split:]
+y_train, y_test = y[:split], y[split:]
+
+# Compute a PCA (eigenfaces) on the face dataset (treated as unlabeled
+# dataset): unsupervised feature extraction / dimensionality reduction
+
+n_components = 150
+
+print "Extracting the top %d eigenfaces" % n_components
+pca = RandomizedPCA(n_components=n_components, whiten=True).fit(X_train)
+
+eigenfaces = pca.components_.T.reshape((n_components, 64, 64))
+
+# project the input data on the eigenfaces orthonormal basis
+X_train_pca = pca.transform(X_train)
+X_test_pca = pca.transform(X_test)
+
+
+# Train a SVM classification model
+
+print "Fitting the classifier to the training set"
+param_grid = {
+ 'C': [1, 5, 10, 100],
+ 'gamma': [0.0001, 0.001, 0.01, 0.1],
+}
+clf = GridSearchCV(SVC(kernel='rbf'), param_grid,
+                   fit_params={'class_weight': 'auto'},
+                   n_jobs=-1)
+clf = clf.fit(X_train_pca, y_train)
+print "Best estimator found by grid search:"
+print clf.best_estimator
+
+
+# Quantitative evaluation of the model quality on the test set
+
+y_pred = clf.predict(X_test_pca)
+print classification_report(y_test, y_pred, labels=selected_target,
+                            class_names=target_names[selected_target])
+
+print confusion_matrix(y_test, y_pred, labels=selected_target)
+
+
+# Qualitative evaluation of the predictions using matplotlib
+
+n_row = 3
+n_col = 4
+
+def title(y_pred, y_test, target_names, i):
+    pred_name = target_names[y_pred[i]].rsplit('_', 1)[-1]
+    true_name = target_names[y_test[i]].rsplit('_', 1)[-1]
+    return 'predicted: %s\ntrue:      %s' % (pred_name, true_name)
+
+
+pl.figure(figsize=(2 * n_col, 2.3 * n_row))
+pl.subplots_adjust(bottom=0, left=.01, right=.99, top=.95, hspace=.15)
+for i in range(n_row * n_col):
+    pl.subplot(n_row, n_col, i + 1)
+    pl.imshow(X_test[i].reshape((64, 64)), cmap=pl.cm.gray)
+    pl.title(title(y_pred, y_test, target_names, i), size=12)
+    pl.xticks(())
+    pl.yticks(())
+
+pl.show()
+
+