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venv/Lib/site-packages/sklearn/linear_model/tests/test_huber.py

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+# Authors: Manoj Kumar mks542@nyu.edu
+# License: BSD 3 clause
+
+import numpy as np
+from scipy import optimize, sparse
+
+from sklearn.utils._testing import assert_almost_equal
+from sklearn.utils._testing import assert_array_equal
+from sklearn.utils._testing import assert_array_almost_equal
+
+from sklearn.datasets import make_regression
+from sklearn.linear_model import (
+    HuberRegressor, LinearRegression, SGDRegressor, Ridge)
+from sklearn.linear_model._huber import _huber_loss_and_gradient
+
+
+def make_regression_with_outliers(n_samples=50, n_features=20):
+    rng = np.random.RandomState(0)
+    # Generate data with outliers by replacing 10% of the samples with noise.
+    X, y = make_regression(
+        n_samples=n_samples, n_features=n_features,
+        random_state=0, noise=0.05)
+
+    # Replace 10% of the sample with noise.
+    num_noise = int(0.1 * n_samples)
+    random_samples = rng.randint(0, n_samples, num_noise)
+    X[random_samples, :] = 2.0 * rng.normal(0, 1, (num_noise, X.shape[1]))
+    return X, y
+
+
+def test_huber_equals_lr_for_high_epsilon():
+    # Test that Ridge matches LinearRegression for large epsilon
+    X, y = make_regression_with_outliers()
+    lr = LinearRegression()
+    lr.fit(X, y)
+    huber = HuberRegressor(epsilon=1e3, alpha=0.0)
+    huber.fit(X, y)
+    assert_almost_equal(huber.coef_, lr.coef_, 3)
+    assert_almost_equal(huber.intercept_, lr.intercept_, 2)
+
+
+def test_huber_max_iter():
+    X, y = make_regression_with_outliers()
+    huber = HuberRegressor(max_iter=1)
+    huber.fit(X, y)
+    assert huber.n_iter_ == huber.max_iter
+
+
+def test_huber_gradient():
+    # Test that the gradient calculated by _huber_loss_and_gradient is correct
+    rng = np.random.RandomState(1)
+    X, y = make_regression_with_outliers()
+    sample_weight = rng.randint(1, 3, (y.shape[0]))
+
+    def loss_func(x, *args):
+        return _huber_loss_and_gradient(x, *args)[0]
+
+    def grad_func(x, *args):
+        return _huber_loss_and_gradient(x, *args)[1]
+
+    # Check using optimize.check_grad that the gradients are equal.
+    for _ in range(5):
+        # Check for both fit_intercept and otherwise.
+        for n_features in [X.shape[1] + 1, X.shape[1] + 2]:
+            w = rng.randn(n_features)
+            w[-1] = np.abs(w[-1])
+            grad_same = optimize.check_grad(
+                loss_func, grad_func, w, X, y, 0.01, 0.1, sample_weight)
+            assert_almost_equal(grad_same, 1e-6, 4)
+
+
+def test_huber_sample_weights():
+    # Test sample_weights implementation in HuberRegressor"""
+
+    X, y = make_regression_with_outliers()
+    huber = HuberRegressor()
+    huber.fit(X, y)
+    huber_coef = huber.coef_
+    huber_intercept = huber.intercept_
+
+    # Rescale coefs before comparing with assert_array_almost_equal to make
+    # sure that the number of decimal places used is somewhat insensitive to
+    # the amplitude of the coefficients and therefore to the scale of the
+    # data and the regularization parameter
+    scale = max(np.mean(np.abs(huber.coef_)),
+                np.mean(np.abs(huber.intercept_)))
+
+    huber.fit(X, y, sample_weight=np.ones(y.shape[0]))
+    assert_array_almost_equal(huber.coef_ / scale, huber_coef / scale)
+    assert_array_almost_equal(huber.intercept_ / scale,
+                              huber_intercept / scale)
+
+    X, y = make_regression_with_outliers(n_samples=5, n_features=20)
+    X_new = np.vstack((X, np.vstack((X[1], X[1], X[3]))))
+    y_new = np.concatenate((y, [y[1]], [y[1]], [y[3]]))
+    huber.fit(X_new, y_new)
+    huber_coef = huber.coef_
+    huber_intercept = huber.intercept_
+    sample_weight = np.ones(X.shape[0])
+    sample_weight[1] = 3
+    sample_weight[3] = 2
+    huber.fit(X, y, sample_weight=sample_weight)
+
+    assert_array_almost_equal(huber.coef_ / scale, huber_coef / scale)
+    assert_array_almost_equal(huber.intercept_ / scale,
+                              huber_intercept / scale)
+
+    # Test sparse implementation with sample weights.
+    X_csr = sparse.csr_matrix(X)
+    huber_sparse = HuberRegressor()
+    huber_sparse.fit(X_csr, y, sample_weight=sample_weight)
+    assert_array_almost_equal(huber_sparse.coef_ / scale,
+                              huber_coef / scale)
+
+
+def test_huber_sparse():
+    X, y = make_regression_with_outliers()
+    huber = HuberRegressor(alpha=0.1)
+    huber.fit(X, y)
+
+    X_csr = sparse.csr_matrix(X)
+    huber_sparse = HuberRegressor(alpha=0.1)
+    huber_sparse.fit(X_csr, y)
+    assert_array_almost_equal(huber_sparse.coef_, huber.coef_)
+    assert_array_equal(huber.outliers_, huber_sparse.outliers_)
+
+
+def test_huber_scaling_invariant():
+    # Test that outliers filtering is scaling independent.
+    X, y = make_regression_with_outliers()
+    huber = HuberRegressor(fit_intercept=False, alpha=0.0, max_iter=100)
+    huber.fit(X, y)
+    n_outliers_mask_1 = huber.outliers_
+    assert not np.all(n_outliers_mask_1)
+
+    huber.fit(X, 2. * y)
+    n_outliers_mask_2 = huber.outliers_
+    assert_array_equal(n_outliers_mask_2, n_outliers_mask_1)
+
+    huber.fit(2. * X, 2. * y)
+    n_outliers_mask_3 = huber.outliers_
+    assert_array_equal(n_outliers_mask_3, n_outliers_mask_1)
+
+
+def test_huber_and_sgd_same_results():
+    # Test they should converge to same coefficients for same parameters
+
+    X, y = make_regression_with_outliers(n_samples=10, n_features=2)
+
+    # Fit once to find out the scale parameter. Scale down X and y by scale
+    # so that the scale parameter is optimized to 1.0
+    huber = HuberRegressor(fit_intercept=False, alpha=0.0, max_iter=100,
+                           epsilon=1.35)
+    huber.fit(X, y)
+    X_scale = X / huber.scale_
+    y_scale = y / huber.scale_
+    huber.fit(X_scale, y_scale)
+    assert_almost_equal(huber.scale_, 1.0, 3)
+
+    sgdreg = SGDRegressor(
+        alpha=0.0, loss="huber", shuffle=True, random_state=0, max_iter=10000,
+        fit_intercept=False, epsilon=1.35, tol=None)
+    sgdreg.fit(X_scale, y_scale)
+    assert_array_almost_equal(huber.coef_, sgdreg.coef_, 1)
+
+
+def test_huber_warm_start():
+    X, y = make_regression_with_outliers()
+    huber_warm = HuberRegressor(
+        alpha=1.0, max_iter=10000, warm_start=True, tol=1e-1)
+
+    huber_warm.fit(X, y)
+    huber_warm_coef = huber_warm.coef_.copy()
+    huber_warm.fit(X, y)
+
+    # SciPy performs the tol check after doing the coef updates, so
+    # these would be almost same but not equal.
+    assert_array_almost_equal(huber_warm.coef_, huber_warm_coef, 1)
+
+    assert huber_warm.n_iter_ == 0
+
+
+def test_huber_better_r2_score():
+    # Test that huber returns a better r2 score than non-outliers"""
+    X, y = make_regression_with_outliers()
+    huber = HuberRegressor(alpha=0.01)
+    huber.fit(X, y)
+    linear_loss = np.dot(X, huber.coef_) + huber.intercept_ - y
+    mask = np.abs(linear_loss) < huber.epsilon * huber.scale_
+    huber_score = huber.score(X[mask], y[mask])
+    huber_outlier_score = huber.score(X[~mask], y[~mask])
+
+    # The Ridge regressor should be influenced by the outliers and hence
+    # give a worse score on the non-outliers as compared to the huber
+    # regressor.
+    ridge = Ridge(alpha=0.01)
+    ridge.fit(X, y)
+    ridge_score = ridge.score(X[mask], y[mask])
+    ridge_outlier_score = ridge.score(X[~mask], y[~mask])
+    assert huber_score > ridge_score
+
+    # The huber model should also fit poorly on the outliers.
+    assert ridge_outlier_score > huber_outlier_score
+
+
+def test_huber_bool():
+    # Test that it does not crash with bool data
+    X, y = make_regression(n_samples=200, n_features=2, noise=4.0,
+                           random_state=0)
+    X_bool = X > 0
+    HuberRegressor().fit(X_bool, y)