test_svm_smote.py

import numpy as np
import pytest
from sklearn.datasets import make_classification
from sklearn.linear_model import LogisticRegression
from sklearn.neighbors import NearestNeighbors
from sklearn.svm import SVC
from sklearn.utils._testing import assert_allclose, assert_array_equal

from imblearn.over_sampling import SVMSMOTE


@pytest.fixture
def data():
    X = np.array(
        [
            [0.11622591, -0.0317206],
            [0.77481731, 0.60935141],
            [1.25192108, -0.22367336],
            [0.53366841, -0.30312976],
            [1.52091956, -0.49283504],
            [-0.28162401, -2.10400981],
            [0.83680821, 1.72827342],
            [0.3084254, 0.33299982],
            [0.70472253, -0.73309052],
            [0.28893132, -0.38761769],
            [1.15514042, 0.0129463],
            [0.88407872, 0.35454207],
            [1.31301027, -0.92648734],
            [-1.11515198, -0.93689695],
            [-0.18410027, -0.45194484],
            [0.9281014, 0.53085498],
            [-0.14374509, 0.27370049],
            [-0.41635887, -0.38299653],
            [0.08711622, 0.93259929],
            [1.70580611, -0.11219234],
        ]
    )
    y = np.array([0, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 0])
    return X, y


def test_svm_smote(data):
    svm_smote = SVMSMOTE(random_state=42)
    svm_smote_nn = SVMSMOTE(
        random_state=42,
        k_neighbors=NearestNeighbors(n_neighbors=6),
        m_neighbors=NearestNeighbors(n_neighbors=11),
        svm_estimator=SVC(gamma="scale", random_state=42),
    )

    X_res_1, y_res_1 = svm_smote.fit_resample(*data)
    X_res_2, y_res_2 = svm_smote_nn.fit_resample(*data)

    assert_allclose(X_res_1, X_res_2)
    assert_array_equal(y_res_1, y_res_2)


def test_svm_smote_not_svm(data):
    """Check that we raise a proper error if passing an estimator that does not
    expose a `support_` fitted attribute."""

    err_msg = "`svm_estimator` is required to exposed a `support_` fitted attribute."
    with pytest.raises(RuntimeError, match=err_msg):
        SVMSMOTE(svm_estimator=LogisticRegression()).fit_resample(*data)


def test_svm_smote_all_noise(data):
    """Check that we raise a proper error message when all support vectors are
    detected as noise and there is nothing that we can do.

    Non-regression test for:
    https://github.com/scikit-learn-contrib/imbalanced-learn/issues/742
    """
    X, y = make_classification(
        n_classes=3,
        class_sep=0.001,
        weights=[0.004, 0.451, 0.545],
        n_informative=3,
        n_redundant=0,
        flip_y=0,
        n_features=3,
        n_clusters_per_class=2,
        n_samples=1000,
        random_state=10,
    )

    with pytest.raises(ValueError, match="SVM-SMOTE is not adapted to your dataset"):
        SVMSMOTE(k_neighbors=4, random_state=42).fit_resample(X, y)