bench_lof.py

"""
============================
LocalOutlierFactor benchmark
============================

A test of LocalOutlierFactor on classical anomaly detection datasets.

Note that LocalOutlierFactor is not meant to predict on a test set and its
performance is assessed in an outlier detection context:
1. The model is trained on the whole dataset which is assumed to contain
outliers.
2. The ROC curve is computed on the same dataset using the knowledge of the
labels.
In this context there is no need to shuffle the dataset because the model
is trained and tested on the whole dataset. The randomness of this benchmark
is only caused by the random selection of anomalies in the SA dataset.

"""

from time import time

import matplotlib.pyplot as plt
import numpy as np

from sklearn.datasets import fetch_covtype, fetch_kddcup99, fetch_openml
from sklearn.metrics import auc, roc_curve
from sklearn.neighbors import LocalOutlierFactor
from sklearn.preprocessing import LabelBinarizer

print(__doc__)

random_state = 2  # to control the random selection of anomalies in SA

# datasets available: ['http', 'smtp', 'SA', 'SF', 'shuttle', 'forestcover']
datasets = ["http", "smtp", "SA", "SF", "shuttle", "forestcover"]

plt.figure()
for dataset_name in datasets:
    # loading and vectorization
    print("loading data")
    if dataset_name in ["http", "smtp", "SA", "SF"]:
        dataset = fetch_kddcup99(
            subset=dataset_name, percent10=True, random_state=random_state
        )
        X = dataset.data
        y = dataset.target

    if dataset_name == "shuttle":
        dataset = fetch_openml("shuttle", as_frame=False)
        X = dataset.data
        y = dataset.target.astype(np.int64)
        # we remove data with label 4
        # normal data are then those of class 1
        s = y != 4
        X = X[s, :]
        y = y[s]
        y = (y != 1).astype(int)

    if dataset_name == "forestcover":
        dataset = fetch_covtype()
        X = dataset.data
        y = dataset.target
        # normal data are those with attribute 2
        # abnormal those with attribute 4
        s = (y == 2) + (y == 4)
        X = X[s, :]
        y = y[s]
        y = (y != 2).astype(int)

    print("vectorizing data")

    if dataset_name == "SF":
        lb = LabelBinarizer()
        x1 = lb.fit_transform(X[:, 1].astype(str))
        X = np.c_[X[:, :1], x1, X[:, 2:]]
        y = (y != b"normal.").astype(int)

    if dataset_name == "SA":
        lb = LabelBinarizer()
        x1 = lb.fit_transform(X[:, 1].astype(str))
        x2 = lb.fit_transform(X[:, 2].astype(str))
        x3 = lb.fit_transform(X[:, 3].astype(str))
        X = np.c_[X[:, :1], x1, x2, x3, X[:, 4:]]
        y = (y != b"normal.").astype(int)

    if dataset_name == "http" or dataset_name == "smtp":
        y = (y != b"normal.").astype(int)

    X = X.astype(float)

    print("LocalOutlierFactor processing...")
    model = LocalOutlierFactor(n_neighbors=20)
    tstart = time()
    model.fit(X)
    fit_time = time() - tstart
    scoring = -model.negative_outlier_factor_  # the lower, the more normal
    fpr, tpr, thresholds = roc_curve(y, scoring)
    AUC = auc(fpr, tpr)
    plt.plot(
        fpr,
        tpr,
        lw=1,
        label="ROC for %s (area = %0.3f, train-time: %0.2fs)"
        % (dataset_name, AUC, fit_time),
    )

plt.xlim([-0.05, 1.05])
plt.ylim([-0.05, 1.05])
plt.xlabel("False Positive Rate")
plt.ylabel("True Positive Rate")
plt.title("Receiver operating characteristic")
plt.legend(loc="lower right")
plt.show()