Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
import numpy as np
from scipy import stats
import matplotlib.pyplot as plt
import matplotlib.font_manager
from sklearn import svm
from sklearn.covariance import EllipticEnvelope
from sklearn.ensemble import IsolationForest
from sklearn.neighbors import LocalOutlierFactor
print(__doc__)
rng = np.random.RandomState(42)
# Example settings
n_samples = 200
outliers_fraction = 0.25
clusters_separation = [0, 1, 2]
# define two outlier detection tools to be compared
classifiers = {
"One-Class SVM": svm.OneClassSVM(nu=0.95 * outliers_fraction + 0.05,
kernel="rbf", gamma=0.1),
"Robust covariance": EllipticEnvelope(contamination=outliers_fraction),
"Isolation Forest": IsolationForest(max_samples=n_samples,
contamination=outliers_fraction,
random_state=rng),
"Local Outlier Factor": LocalOutlierFactor(
n_neighbors=35,
contamination=outliers_fraction)}
# Compare given classifiers under given settings
xx, yy = np.meshgrid(np.linspace(-7, 7, 100), np.linspace(-7, 7, 100))
n_inliers = int((1. - outliers_fraction) * n_samples)
n_outliers = int(outliers_fraction * n_samples)
ground_truth = np.ones(n_samples, dtype=int)
ground_truth[-n_outliers:] = -1
# Fit the problem with varying cluster separation
for i, offset in enumerate(clusters_separation):
np.random.seed(42)
# Data generation
X1 = 0.3 * np.random.randn(n_inliers // 2, 2) - offset
X2 = 0.3 * np.random.randn(n_inliers // 2, 2) + offset
X = np.r_[X1, X2]
# Add outliers
X = np.r_[X, np.random.uniform(low=-6, high=6, size=(n_outliers, 2))]
# Fit the model
plt.figure(figsize=(9, 7))
for i, (clf_name, clf) in enumerate(classifiers.items()):
# fit the data and tag outliers
if clf_name == "Local Outlier Factor":
y_pred = clf.fit_predict(X)
scores_pred = clf.negative_outlier_factor_
else:
clf.fit(X)
scores_pred = clf.decision_function(X)
y_pred = clf.predict(X)
threshold = stats.scoreatpercentile(scores_pred,
100 * outliers_fraction)
n_errors = (y_pred != ground_truth).sum()
# plot the levels lines and the points
if clf_name == "Local Outlier Factor":
# decision_function is private for LOF
Z = clf._decision_function(np.c_[xx.ravel(), yy.ravel()])
else:
Z = clf.decision_function(np.c_[xx.ravel(), yy.ravel()])
Z = Z.reshape(xx.shape)
subplot = plt.subplot(2, 2, i + 1)
subplot.contourf(xx, yy, Z, levels=np.linspace(Z.min(), threshold, 7),
cmap=plt.cm.Blues_r)
a = subplot.contour(xx, yy, Z, levels=[threshold],
linewidths=2, colors='red')
subplot.contourf(xx, yy, Z, levels=[threshold, Z.max()],
colors='orange')
b = subplot.scatter(X[:-n_outliers, 0], X[:-n_outliers, 1], c='white',
s=20, edgecolor='k')
c = subplot.scatter(X[-n_outliers:, 0], X[-n_outliers:, 1], c='black',
s=20, edgecolor='k')
subplot.axis('tight')
subplot.legend(
[a.collections[0], b, c],
['learned decision function', 'true inliers', 'true outliers'],
prop=matplotlib.font_manager.FontProperties(size=10),
loc='lower right')
subplot.set_xlabel("%d. %s (errors: %d)" % (i + 1, clf_name, n_errors))
subplot.set_xlim((-7, 7))
subplot.set_ylim((-7, 7))
plt.subplots_adjust(0.04, 0.1, 0.96, 0.94, 0.1, 0.26)
plt.suptitle("Outlier detection")
plt.show()
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.