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# Authors: Manoj Kumar mks542@nyu.edu
# License: BSD 3 clause
import numpy as np
import pytest
from scipy import optimize
from sklearn.datasets import make_regression
from sklearn.linear_model import HuberRegressor, LinearRegression, Ridge, SGDRegressor
from sklearn.linear_model._huber import _huber_loss_and_gradient
from sklearn.utils._testing import (
assert_almost_equal,
assert_array_almost_equal,
assert_array_equal,
)
from sklearn.utils.fixes import CSR_CONTAINERS
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)
@pytest.mark.parametrize("csr_container", CSR_CONTAINERS)
def test_huber_sample_weights(csr_container):
# 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 = csr_container(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)
@pytest.mark.parametrize("csr_container", CSR_CONTAINERS)
def test_huber_sparse(csr_container):
X, y = make_regression_with_outliers()
huber = HuberRegressor(alpha=0.1)
huber.fit(X, y)
X_csr = csr_container(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)
huber.fit(X, y)
n_outliers_mask_1 = huber.outliers_
assert not np.all(n_outliers_mask_1)
huber.fit(X, 2.0 * y)
n_outliers_mask_2 = huber.outliers_
assert_array_equal(n_outliers_mask_2, n_outliers_mask_1)
huber.fit(2.0 * X, 2.0 * 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, 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)
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