import re
import warnings
from functools import partial
from itertools import chain, permutations, product

import numpy as np
import pytest
from scipy import linalg
from scipy.spatial.distance import hamming as sp_hamming
from scipy.stats import bernoulli

from sklearn import datasets, svm
from sklearn.datasets import make_multilabel_classification
from sklearn.exceptions import UndefinedMetricWarning
from sklearn.metrics import (
    accuracy_score,
    average_precision_score,
    balanced_accuracy_score,
    brier_score_loss,
    class_likelihood_ratios,
    classification_report,
    cohen_kappa_score,
    confusion_matrix,
    f1_score,
    fbeta_score,
    hamming_loss,
    hinge_loss,
    jaccard_score,
    log_loss,
    make_scorer,
    matthews_corrcoef,
    multilabel_confusion_matrix,
    precision_recall_fscore_support,
    precision_score,
    recall_score,
    zero_one_loss,
)
from sklearn.metrics._classification import _check_targets, d2_log_loss_score
from sklearn.model_selection import cross_val_score
from sklearn.preprocessing import LabelBinarizer, label_binarize
from sklearn.tree import DecisionTreeClassifier
from sklearn.utils._mocking import MockDataFrame
from sklearn.utils._testing import (
    assert_allclose,
    assert_almost_equal,
    assert_array_almost_equal,
    assert_array_equal,
    ignore_warnings,
)
from sklearn.utils.extmath import _nanaverage
from sklearn.utils.fixes import CSC_CONTAINERS, CSR_CONTAINERS
from sklearn.utils.validation import check_random_state

###############################################################################
# Utilities for testing


def make_prediction(dataset=None, binary=False):
    """Make some classification predictions on a toy dataset using a SVC

    If binary is True restrict to a binary classification problem instead of a
    multiclass classification problem
    """

    if dataset is None:
        # import some data to play with
        dataset = datasets.load_iris()

    X = dataset.data
    y = dataset.target

    if binary:
        # restrict to a binary classification task
        X, y = X[y < 2], y[y < 2]

    n_samples, n_features = X.shape
    p = np.arange(n_samples)

    rng = check_random_state(37)
    rng.shuffle(p)
    X, y = X[p], y[p]
    half = int(n_samples / 2)

    # add noisy features to make the problem harder and avoid perfect results
    rng = np.random.RandomState(0)
    X = np.c_[X, rng.randn(n_samples, 200 * n_features)]

    # run classifier, get class probabilities and label predictions
    clf = svm.SVC(kernel="linear", probability=True, random_state=0)
    y_pred_proba = clf.fit(X[:half], y[:half]).predict_proba(X[half:])

    if binary:
        # only interested in probabilities of the positive case
        # XXX: do we really want a special API for the binary case?
        y_pred_proba = y_pred_proba[:, 1]

    y_pred = clf.predict(X[half:])
    y_true = y[half:]
    return y_true, y_pred, y_pred_proba


###############################################################################
# Tests


def test_classification_report_dictionary_output():
    # Test performance report with dictionary output
    iris = datasets.load_iris()
    y_true, y_pred, _ = make_prediction(dataset=iris, binary=False)

    # print classification report with class names
    expected_report = {
        "setosa": {
            "precision": 0.82608695652173914,
            "recall": 0.79166666666666663,
            "f1-score": 0.8085106382978724,
            "support": 24,
        },
        "versicolor": {
            "precision": 0.33333333333333331,
            "recall": 0.096774193548387094,
            "f1-score": 0.15000000000000002,
            "support": 31,
        },
        "virginica": {
            "precision": 0.41860465116279072,
            "recall": 0.90000000000000002,
            "f1-score": 0.57142857142857151,
            "support": 20,
        },
        "macro avg": {
            "f1-score": 0.5099797365754813,
            "precision": 0.5260083136726211,
            "recall": 0.596146953405018,
            "support": 75,
        },
        "accuracy": 0.5333333333333333,
        "weighted avg": {
            "f1-score": 0.47310435663627154,
            "precision": 0.5137535108414785,
            "recall": 0.5333333333333333,
            "support": 75,
        },
    }

    report = classification_report(
        y_true,
        y_pred,
        labels=np.arange(len(iris.target_names)),
        target_names=iris.target_names,
        output_dict=True,
    )

    # assert the 2 dicts are equal.
    assert report.keys() == expected_report.keys()
    for key in expected_report:
        if key == "accuracy":
            assert isinstance(report[key], float)
            assert report[key] == expected_report[key]
        else:
            assert report[key].keys() == expected_report[key].keys()
            for metric in expected_report[key]:
                assert_almost_equal(expected_report[key][metric], report[key][metric])

    assert isinstance(expected_report["setosa"]["precision"], float)
    assert isinstance(expected_report["macro avg"]["precision"], float)
    assert isinstance(expected_report["setosa"]["support"], int)
    assert isinstance(expected_report["macro avg"]["support"], int)


def test_classification_report_output_dict_empty_input():
    report = classification_report(y_true=[], y_pred=[], output_dict=True)
    expected_report = {
        "accuracy": 0.0,
        "macro avg": {
            "f1-score": np.nan,
            "precision": np.nan,
            "recall": np.nan,
            "support": 0,
        },
        "weighted avg": {
            "f1-score": np.nan,
            "precision": np.nan,
            "recall": np.nan,
            "support": 0,
        },
    }
    assert isinstance(report, dict)
    # assert the 2 dicts are equal.
    assert report.keys() == expected_report.keys()
    for key in expected_report:
        if key == "accuracy":
            assert isinstance(report[key], float)
            assert report[key] == expected_report[key]
        else:
            assert report[key].keys() == expected_report[key].keys()
            for metric in expected_report[key]:
                assert_almost_equal(expected_report[key][metric], report[key][metric])


@pytest.mark.parametrize("zero_division", ["warn", 0, 1, np.nan])
def test_classification_report_zero_division_warning(zero_division):
    y_true, y_pred = ["a", "b", "c"], ["a", "b", "d"]
    with warnings.catch_warnings(record=True) as record:
        classification_report(
            y_true, y_pred, zero_division=zero_division, output_dict=True
        )
        if zero_division == "warn":
            assert len(record) > 1
            for item in record:
                msg = "Use `zero_division` parameter to control this behavior."
                assert msg in str(item.message)
        else:
            assert not record


@pytest.mark.parametrize(
    "labels, show_micro_avg", [([0], True), ([0, 1], False), ([0, 1, 2], False)]
)
def test_classification_report_labels_subset_superset(labels, show_micro_avg):
    """Check the behaviour of passing `labels` as a superset or subset of the labels.
    WHen a superset, we expect to show the "accuracy" in the report while it should be
    the micro-averaging if this is a subset.

    Non-regression test for:
    https://github.com/scikit-learn/scikit-learn/issues/27927
    """

    y_true, y_pred = [0, 1], [0, 1]

    report = classification_report(y_true, y_pred, labels=labels, output_dict=True)
    if show_micro_avg:
        assert "micro avg" in report
        assert "accuracy" not in report
    else:  # accuracy should be shown
        assert "accuracy" in report
        assert "micro avg" not in report


def test_multilabel_accuracy_score_subset_accuracy():
    # Dense label indicator matrix format
    y1 = np.array([[0, 1, 1], [1, 0, 1]])
    y2 = np.array([[0, 0, 1], [1, 0, 1]])

    assert accuracy_score(y1, y2) == 0.5
    assert accuracy_score(y1, y1) == 1
    assert accuracy_score(y2, y2) == 1
    assert accuracy_score(y2, np.logical_not(y2)) == 0
    assert accuracy_score(y1, np.logical_not(y1)) == 0
    assert accuracy_score(y1, np.zeros(y1.shape)) == 0
    assert accuracy_score(y2, np.zeros(y1.shape)) == 0


def test_precision_recall_f1_score_binary():
    # Test Precision Recall and F1 Score for binary classification task
    y_true, y_pred, _ = make_prediction(binary=True)

    # detailed measures for each class
    p, r, f, s = precision_recall_fscore_support(y_true, y_pred, average=None)
    assert_array_almost_equal(p, [0.73, 0.85], 2)
    assert_array_almost_equal(r, [0.88, 0.68], 2)
    assert_array_almost_equal(f, [0.80, 0.76], 2)
    assert_array_equal(s, [25, 25])

    # individual scoring function that can be used for grid search: in the
    # binary class case the score is the value of the measure for the positive
    # class (e.g. label == 1). This is deprecated for average != 'binary'.
    for kwargs in [{}, {"average": "binary"}]:
        with warnings.catch_warnings():
            warnings.simplefilter("error")

            ps = precision_score(y_true, y_pred, **kwargs)
            assert_array_almost_equal(ps, 0.85, 2)

            rs = recall_score(y_true, y_pred, **kwargs)
            assert_array_almost_equal(rs, 0.68, 2)

            fs = f1_score(y_true, y_pred, **kwargs)
            assert_array_almost_equal(fs, 0.76, 2)

            assert_almost_equal(
                fbeta_score(y_true, y_pred, beta=2, **kwargs),
                (1 + 2**2) * ps * rs / (2**2 * ps + rs),
                2,
            )


@pytest.mark.filterwarnings(r"ignore::sklearn.exceptions.UndefinedMetricWarning")
def test_precision_recall_f_binary_single_class():
    # Test precision, recall and F-scores behave with a single positive or
    # negative class
    # Such a case may occur with non-stratified cross-validation
    assert 1.0 == precision_score([1, 1], [1, 1])
    assert 1.0 == recall_score([1, 1], [1, 1])
    assert 1.0 == f1_score([1, 1], [1, 1])
    assert 1.0 == fbeta_score([1, 1], [1, 1], beta=0)

    assert 0.0 == precision_score([-1, -1], [-1, -1])
    assert 0.0 == recall_score([-1, -1], [-1, -1])
    assert 0.0 == f1_score([-1, -1], [-1, -1])
    assert 0.0 == fbeta_score([-1, -1], [-1, -1], beta=float("inf"))
    assert fbeta_score([-1, -1], [-1, -1], beta=float("inf")) == pytest.approx(
        fbeta_score([-1, -1], [-1, -1], beta=1e5)
    )


@pytest.mark.filterwarnings(r"ignore::sklearn.exceptions.UndefinedMetricWarning")
def test_precision_recall_f_extra_labels():
    # Test handling of explicit additional (not in input) labels to PRF
    y_true = [1, 3, 3, 2]
    y_pred = [1, 1, 3, 2]
    y_true_bin = label_binarize(y_true, classes=np.arange(5))
    y_pred_bin = label_binarize(y_pred, classes=np.arange(5))
    data = [(y_true, y_pred), (y_true_bin, y_pred_bin)]

    for i, (y_true, y_pred) in enumerate(data):
        # No average: zeros in array
        actual = recall_score(y_true, y_pred, labels=[0, 1, 2, 3, 4], average=None)
        assert_array_almost_equal([0.0, 1.0, 1.0, 0.5, 0.0], actual)

        # Macro average is changed
        actual = recall_score(y_true, y_pred, labels=[0, 1, 2, 3, 4], average="macro")
        assert_array_almost_equal(np.mean([0.0, 1.0, 1.0, 0.5, 0.0]), actual)

        # No effect otherwise
        for average in ["micro", "weighted", "samples"]:
            if average == "samples" and i == 0:
                continue
            assert_almost_equal(
                recall_score(y_true, y_pred, labels=[0, 1, 2, 3, 4], average=average),
                recall_score(y_true, y_pred, labels=None, average=average),
            )

    # Error when introducing invalid label in multilabel case
    # (although it would only affect performance if average='macro'/None)
    for average in [None, "macro", "micro", "samples"]:
        with pytest.raises(ValueError):
            recall_score(y_true_bin, y_pred_bin, labels=np.arange(6), average=average)
        with pytest.raises(ValueError):
            recall_score(
                y_true_bin, y_pred_bin, labels=np.arange(-1, 4), average=average
            )

    # tests non-regression on issue #10307
    y_true = np.array([[0, 1, 1], [1, 0, 0]])
    y_pred = np.array([[1, 1, 1], [1, 0, 1]])
    p, r, f, _ = precision_recall_fscore_support(
        y_true, y_pred, average="samples", labels=[0, 1]
    )
    assert_almost_equal(np.array([p, r, f]), np.array([3 / 4, 1, 5 / 6]))


@pytest.mark.filterwarnings(r"ignore::sklearn.exceptions.UndefinedMetricWarning")
def test_precision_recall_f_ignored_labels():
    # Test a subset of labels may be requested for PRF
    y_true = [1, 1, 2, 3]
    y_pred = [1, 3, 3, 3]
    y_true_bin = label_binarize(y_true, classes=np.arange(5))
    y_pred_bin = label_binarize(y_pred, classes=np.arange(5))
    data = [(y_true, y_pred), (y_true_bin, y_pred_bin)]

    for i, (y_true, y_pred) in enumerate(data):
        recall_13 = partial(recall_score, y_true, y_pred, labels=[1, 3])
        recall_all = partial(recall_score, y_true, y_pred, labels=None)

        assert_array_almost_equal([0.5, 1.0], recall_13(average=None))
        assert_almost_equal((0.5 + 1.0) / 2, recall_13(average="macro"))
        assert_almost_equal((0.5 * 2 + 1.0 * 1) / 3, recall_13(average="weighted"))
        assert_almost_equal(2.0 / 3, recall_13(average="micro"))

        # ensure the above were meaningful tests:
        for average in ["macro", "weighted", "micro"]:
            assert recall_13(average=average) != recall_all(average=average)


def test_average_precision_score_non_binary_class():
    """Test multiclass-multiouptut for `average_precision_score`."""
    y_true = np.array(
        [
            [2, 2, 1],
            [1, 2, 0],
            [0, 1, 2],
            [1, 2, 1],
            [2, 0, 1],
            [1, 2, 1],
        ]
    )
    y_score = np.array(
        [
            [0.7, 0.2, 0.1],
            [0.4, 0.3, 0.3],
            [0.1, 0.8, 0.1],
            [0.2, 0.3, 0.5],
            [0.4, 0.4, 0.2],
            [0.1, 0.2, 0.7],
        ]
    )
    err_msg = "multiclass-multioutput format is not supported"
    with pytest.raises(ValueError, match=err_msg):
        average_precision_score(y_true, y_score, pos_label=2)


@pytest.mark.parametrize(
    "y_true, y_score",
    [
        (
            [0, 0, 1, 2],
            np.array(
                [
                    [0.7, 0.2, 0.1],
                    [0.4, 0.3, 0.3],
                    [0.1, 0.8, 0.1],
                    [0.2, 0.3, 0.5],
                ]
            ),
        ),
        (
            [0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1],
            [0, 0.1, 0.1, 0.4, 0.5, 0.6, 0.6, 0.9, 0.9, 1, 1],
        ),
    ],
)
def test_average_precision_score_duplicate_values(y_true, y_score):
    """
    Duplicate values with precision-recall require a different
    processing than when computing the AUC of a ROC, because the
    precision-recall curve is a decreasing curve
    The following situation corresponds to a perfect
    test statistic, the average_precision_score should be 1.
    """
    assert average_precision_score(y_true, y_score) == 1


@pytest.mark.parametrize(
    "y_true, y_score",
    [
        (
            [2, 2, 1, 1, 0],
            np.array(
                [
                    [0.2, 0.3, 0.5],
                    [0.2, 0.3, 0.5],
                    [0.4, 0.5, 0.3],
                    [0.4, 0.5, 0.3],
                    [0.8, 0.5, 0.3],
                ]
            ),
        ),
        (
            [0, 1, 1],
            [0.5, 0.5, 0.6],
        ),
    ],
)
def test_average_precision_score_tied_values(y_true, y_score):
    # Here if we go from left to right in y_true, the 0 values are
    # separated from the 1 values, so it appears that we've
    # correctly sorted our classifications. But in fact the first two
    # values have the same score (0.5) and so the first two values
    # could be swapped around, creating an imperfect sorting. This
    # imperfection should come through in the end score, making it less
    # than one.
    assert average_precision_score(y_true, y_score) != 1.0


def test_precision_recall_f_unused_pos_label():
    # Check warning that pos_label unused when set to non-default value
    # but average != 'binary'; even if data is binary.

    msg = (
        r"Note that pos_label \(set to 2\) is "
        r"ignored when average != 'binary' \(got 'macro'\). You "
        r"may use labels=\[pos_label\] to specify a single "
        "positive class."
    )
    with pytest.warns(UserWarning, match=msg):
        precision_recall_fscore_support(
            [1, 2, 1], [1, 2, 2], pos_label=2, average="macro"
        )


def test_confusion_matrix_binary():
    # Test confusion matrix - binary classification case
    y_true, y_pred, _ = make_prediction(binary=True)

    def test(y_true, y_pred):
        cm = confusion_matrix(y_true, y_pred)
        assert_array_equal(cm, [[22, 3], [8, 17]])

        tp, fp, fn, tn = cm.flatten()
        num = tp * tn - fp * fn
        den = np.sqrt((tp + fp) * (tp + fn) * (tn + fp) * (tn + fn))

        true_mcc = 0 if den == 0 else num / den
        mcc = matthews_corrcoef(y_true, y_pred)
        assert_array_almost_equal(mcc, true_mcc, decimal=2)
        assert_array_almost_equal(mcc, 0.57, decimal=2)

    test(y_true, y_pred)
    test([str(y) for y in y_true], [str(y) for y in y_pred])


def test_multilabel_confusion_matrix_binary():
    # Test multilabel confusion matrix - binary classification case
    y_true, y_pred, _ = make_prediction(binary=True)

    def test(y_true, y_pred):
        cm = multilabel_confusion_matrix(y_true, y_pred)
        assert_array_equal(cm, [[[17, 8], [3, 22]], [[22, 3], [8, 17]]])

    test(y_true, y_pred)
    test([str(y) for y in y_true], [str(y) for y in y_pred])


def test_multilabel_confusion_matrix_multiclass():
    # Test multilabel confusion matrix - multi-class case
    y_true, y_pred, _ = make_prediction(binary=False)

    def test(y_true, y_pred, string_type=False):
        # compute confusion matrix with default labels introspection
        cm = multilabel_confusion_matrix(y_true, y_pred)
        assert_array_equal(
            cm, [[[47, 4], [5, 19]], [[38, 6], [28, 3]], [[30, 25], [2, 18]]]
        )

        # compute confusion matrix with explicit label ordering
        labels = ["0", "2", "1"] if string_type else [0, 2, 1]
        cm = multilabel_confusion_matrix(y_true, y_pred, labels=labels)
        assert_array_equal(
            cm, [[[47, 4], [5, 19]], [[30, 25], [2, 18]], [[38, 6], [28, 3]]]
        )

        # compute confusion matrix with super set of present labels
        labels = ["0", "2", "1", "3"] if string_type else [0, 2, 1, 3]
        cm = multilabel_confusion_matrix(y_true, y_pred, labels=labels)
        assert_array_equal(
            cm,
            [
                [[47, 4], [5, 19]],
                [[30, 25], [2, 18]],
                [[38, 6], [28, 3]],
                [[75, 0], [0, 0]],
            ],
        )

    test(y_true, y_pred)
    test([str(y) for y in y_true], [str(y) for y in y_pred], string_type=True)


@pytest.mark.parametrize("csc_container", CSC_CONTAINERS)
@pytest.mark.parametrize("csr_container", CSR_CONTAINERS)
def test_multilabel_confusion_matrix_multilabel(csc_container, csr_container):
    # Test multilabel confusion matrix - multilabel-indicator case

    y_true = np.array([[1, 0, 1], [0, 1, 0], [1, 1, 0]])
    y_pred = np.array([[1, 0, 0], [0, 1, 1], [0, 0, 1]])
    y_true_csr = csr_container(y_true)
    y_pred_csr = csr_container(y_pred)
    y_true_csc = csc_container(y_true)
    y_pred_csc = csc_container(y_pred)

    # cross test different types
    sample_weight = np.array([2, 1, 3])
    real_cm = [[[1, 0], [1, 1]], [[1, 0], [1, 1]], [[0, 2], [1, 0]]]
    trues = [y_true, y_true_csr, y_true_csc]
    preds = [y_pred, y_pred_csr, y_pred_csc]

    for y_true_tmp in trues:
        for y_pred_tmp in preds:
            cm = multilabel_confusion_matrix(y_true_tmp, y_pred_tmp)
            assert_array_equal(cm, real_cm)

    # test support for samplewise
    cm = multilabel_confusion_matrix(y_true, y_pred, samplewise=True)
    assert_array_equal(cm, [[[1, 0], [1, 1]], [[1, 1], [0, 1]], [[0, 1], [2, 0]]])

    # test support for labels
    cm = multilabel_confusion_matrix(y_true, y_pred, labels=[2, 0])
    assert_array_equal(cm, [[[0, 2], [1, 0]], [[1, 0], [1, 1]]])

    # test support for labels with samplewise
    cm = multilabel_confusion_matrix(y_true, y_pred, labels=[2, 0], samplewise=True)
    assert_array_equal(cm, [[[0, 0], [1, 1]], [[1, 1], [0, 0]], [[0, 1], [1, 0]]])

    # test support for sample_weight with sample_wise
    cm = multilabel_confusion_matrix(
        y_true, y_pred, sample_weight=sample_weight, samplewise=True
    )
    assert_array_equal(cm, [[[2, 0], [2, 2]], [[1, 1], [0, 1]], [[0, 3], [6, 0]]])


def test_multilabel_confusion_matrix_errors():
    y_true = np.array([[1, 0, 1], [0, 1, 0], [1, 1, 0]])
    y_pred = np.array([[1, 0, 0], [0, 1, 1], [0, 0, 1]])

    # Bad sample_weight
    with pytest.raises(ValueError, match="inconsistent numbers of samples"):
        multilabel_confusion_matrix(y_true, y_pred, sample_weight=[1, 2])
    with pytest.raises(ValueError, match="should be a 1d array"):
        multilabel_confusion_matrix(
            y_true, y_pred, sample_weight=[[1, 2, 3], [2, 3, 4], [3, 4, 5]]
        )

    # Bad labels
    err_msg = r"All labels must be in \[0, n labels\)"
    with pytest.raises(ValueError, match=err_msg):
        multilabel_confusion_matrix(y_true, y_pred, labels=[-1])
    err_msg = r"All labels must be in \[0, n labels\)"
    with pytest.raises(ValueError, match=err_msg):
        multilabel_confusion_matrix(y_true, y_pred, labels=[3])

    # Using samplewise outside multilabel
    with pytest.raises(ValueError, match="Samplewise metrics"):
        multilabel_confusion_matrix([0, 1, 2], [1, 2, 0], samplewise=True)

    # Bad y_type
    err_msg = "multiclass-multioutput is not supported"
    with pytest.raises(ValueError, match=err_msg):
        multilabel_confusion_matrix([[0, 1, 2], [2, 1, 0]], [[1, 2, 0], [1, 0, 2]])


@pytest.mark.parametrize(
    "normalize, cm_dtype, expected_results",
    [
        ("true", "f", 0.333333333),
        ("pred", "f", 0.333333333),
        ("all", "f", 0.1111111111),
        (None, "i", 2),
    ],
)
def test_confusion_matrix_normalize(normalize, cm_dtype, expected_results):
    y_test = [0, 1, 2] * 6
    y_pred = list(chain(*permutations([0, 1, 2])))
    cm = confusion_matrix(y_test, y_pred, normalize=normalize)
    assert_allclose(cm, expected_results)
    assert cm.dtype.kind == cm_dtype


def test_confusion_matrix_normalize_single_class():
    y_test = [0, 0, 0, 0, 1, 1, 1, 1]
    y_pred = [0, 0, 0, 0, 0, 0, 0, 0]

    cm_true = confusion_matrix(y_test, y_pred, normalize="true")
    assert cm_true.sum() == pytest.approx(2.0)

    # additionally check that no warnings are raised due to a division by zero
    with warnings.catch_warnings():
        warnings.simplefilter("error", RuntimeWarning)
        cm_pred = confusion_matrix(y_test, y_pred, normalize="pred")

    assert cm_pred.sum() == pytest.approx(1.0)

    with warnings.catch_warnings():
        warnings.simplefilter("error", RuntimeWarning)
        confusion_matrix(y_pred, y_test, normalize="true")


def test_confusion_matrix_single_label():
    """Test `confusion_matrix` warns when only one label found."""
    y_test = [0, 0, 0, 0]
    y_pred = [0, 0, 0, 0]

    with pytest.warns(UserWarning, match="A single label was found in"):
        confusion_matrix(y_pred, y_test)


@pytest.mark.parametrize(
    "params, warn_msg",
    [
        # When `fp == 0` and `tp != 0`, LR+ is undefined
        (
            {
                "y_true": np.array([1, 1, 1, 0, 0, 0]),
                "y_pred": np.array([1, 1, 1, 0, 0, 0]),
            },
            "`positive_likelihood_ratio` is ill-defined and set to `np.nan`.",
        ),
        # When `fp == 0` and `tp == 0`, LR+ is undefined
        (
            {
                "y_true": np.array([1, 1, 1, 0, 0, 0]),
                "y_pred": np.array([0, 0, 0, 0, 0, 0]),
            },
            (
                "No samples were predicted for the positive class and "
                "`positive_likelihood_ratio` is set to `np.nan`."
            ),
        ),
        # When `tn == 0`, LR- is undefined
        (
            {
                "y_true": np.array([1, 1, 1, 0, 0, 0]),
                "y_pred": np.array([0, 0, 0, 1, 1, 1]),
            },
            "`negative_likelihood_ratio` is ill-defined and set to `np.nan`.",
        ),
        # When `tp + fn == 0` both ratios are undefined
        (
            {
                "y_true": np.array([0, 0, 0, 0, 0, 0]),
                "y_pred": np.array([1, 1, 1, 0, 0, 0]),
            },
            "No samples of the positive class are present in `y_true`.",
        ),
    ],
)
def test_likelihood_ratios_warnings(params, warn_msg):
    # likelihood_ratios must raise warnings when at
    # least one of the ratios is ill-defined.

    with pytest.warns(UserWarning, match=warn_msg):
        class_likelihood_ratios(**params)


@pytest.mark.parametrize(
    "params, err_msg",
    [
        (
            {
                "y_true": np.array([0, 1, 0, 1, 0]),
                "y_pred": np.array([1, 1, 0, 0, 2]),
            },
            (
                "class_likelihood_ratios only supports binary classification "
                "problems, got targets of type: multiclass"
            ),
        ),
    ],
)
def test_likelihood_ratios_errors(params, err_msg):
    # likelihood_ratios must raise error when attempting
    # non-binary classes to avoid Simpson's paradox
    with pytest.raises(ValueError, match=err_msg):
        class_likelihood_ratios(**params)


def test_likelihood_ratios():
    # Build confusion matrix with tn=9, fp=8, fn=1, tp=2,
    # sensitivity=2/3, specificity=9/17, prevalence=3/20,
    # LR+=34/24, LR-=17/27
    y_true = np.array([1] * 3 + [0] * 17)
    y_pred = np.array([1] * 2 + [0] * 10 + [1] * 8)

    pos, neg = class_likelihood_ratios(y_true, y_pred)
    assert_allclose(pos, 34 / 24)
    assert_allclose(neg, 17 / 27)

    # Build limit case with y_pred = y_true
    pos, neg = class_likelihood_ratios(y_true, y_true)
    assert_array_equal(pos, np.nan * 2)
    assert_allclose(neg, np.zeros(2), rtol=1e-12)

    # Ignore last 5 samples to get tn=9, fp=3, fn=1, tp=2,
    # sensitivity=2/3, specificity=9/12, prevalence=3/20,
    # LR+=24/9, LR-=12/27
    sample_weight = np.array([1.0] * 15 + [0.0] * 5)
    pos, neg = class_likelihood_ratios(y_true, y_pred, sample_weight=sample_weight)
    assert_allclose(pos, 24 / 9)
    assert_allclose(neg, 12 / 27)


# TODO(1.9): remove test
@pytest.mark.parametrize("raise_warning", [True, False])
def test_likelihood_ratios_raise_warning_deprecation(raise_warning):
    """Test that class_likelihood_ratios raises a `FutureWarning` when `raise_warning`
    param is set."""
    y_true = np.array([1, 0])
    y_pred = np.array([1, 0])

    msg = "`raise_warning` was deprecated in version 1.7 and will be removed in 1.9."
    with pytest.warns(FutureWarning, match=msg):
        class_likelihood_ratios(y_true, y_pred, raise_warning=raise_warning)


def test_likelihood_ratios_replace_undefined_by_worst():
    """Test that class_likelihood_ratios returns the worst scores `1.0` for both LR+ and
    LR- when `replace_undefined_by=1` is set."""
    # This data causes fp=0 (0 false positives) in the confusion_matrix and a division
    # by zero that affects the positive_likelihood_ratio:
    y_true = np.array([1, 1, 0])
    y_pred = np.array([1, 0, 0])

    positive_likelihood_ratio, _ = class_likelihood_ratios(
        y_true, y_pred, replace_undefined_by=1
    )
    assert positive_likelihood_ratio == pytest.approx(1.0)

    # This data causes tn=0 (0 true negatives) in the confusion_matrix and a division
    # by zero that affects the negative_likelihood_ratio:
    y_true = np.array([1, 0, 0])
    y_pred = np.array([1, 1, 1])

    _, negative_likelihood_ratio = class_likelihood_ratios(
        y_true, y_pred, replace_undefined_by=1
    )
    assert negative_likelihood_ratio == pytest.approx(1.0)


@pytest.mark.parametrize(
    "replace_undefined_by",
    [
        {"LR+": 0.0},
        {"LR-": 0.0},
        {"LR+": -5.0, "LR-": 0.0},
        {"LR+": 1.0, "LR-": "nan"},
        {"LR+": 0.0, "LR-": 0.0},
        {"LR+": 1.0, "LR-": 2.0},
    ],
)
def test_likelihood_ratios_wrong_dict_replace_undefined_by(replace_undefined_by):
    """Test that class_likelihood_ratios raises a `ValueError` if the input dict for
    `replace_undefined_by` is in the wrong format or contains impossible values."""
    y_true = np.array([1, 0])
    y_pred = np.array([1, 0])

    msg = "The dictionary passed as `replace_undefined_by` needs to be in the form"
    with pytest.raises(ValueError, match=msg):
        class_likelihood_ratios(
            y_true, y_pred, replace_undefined_by=replace_undefined_by
        )


@pytest.mark.parametrize(
    "replace_undefined_by, expected",
    [
        ({"LR+": 1.0, "LR-": 1.0}, 1.0),
        ({"LR+": np.inf, "LR-": 0.0}, np.inf),
        ({"LR+": 2.0, "LR-": 0.0}, 2.0),
        ({"LR+": np.nan, "LR-": np.nan}, np.nan),
        (np.nan, np.nan),
    ],
)
def test_likelihood_ratios_replace_undefined_by_0_fp(replace_undefined_by, expected):
    """Test that the `replace_undefined_by` param returns the right value for the
    positive_likelihood_ratio as defined by the user."""
    # This data causes fp=0 (0 false positives) in the confusion_matrix and a division
    # by zero that affects the positive_likelihood_ratio:
    y_true = np.array([1, 1, 0])
    y_pred = np.array([1, 0, 0])

    positive_likelihood_ratio, _ = class_likelihood_ratios(
        y_true, y_pred, replace_undefined_by=replace_undefined_by
    )

    if np.isnan(expected):
        assert np.isnan(positive_likelihood_ratio)
    else:
        assert positive_likelihood_ratio == pytest.approx(expected)


@pytest.mark.parametrize(
    "replace_undefined_by, expected",
    [
        ({"LR+": 1.0, "LR-": 1.0}, 1.0),
        ({"LR+": np.inf, "LR-": 0.0}, 0.0),
        ({"LR+": np.inf, "LR-": 0.5}, 0.5),
        ({"LR+": np.nan, "LR-": np.nan}, np.nan),
        (np.nan, np.nan),
    ],
)
def test_likelihood_ratios_replace_undefined_by_0_tn(replace_undefined_by, expected):
    """Test that the `replace_undefined_by` param returns the right value for the
    negative_likelihood_ratio as defined by the user."""
    # This data causes tn=0 (0 true negatives) in the confusion_matrix and a division
    # by zero that affects the negative_likelihood_ratio:
    y_true = np.array([1, 0, 0])
    y_pred = np.array([1, 1, 1])

    _, negative_likelihood_ratio = class_likelihood_ratios(
        y_true, y_pred, replace_undefined_by=replace_undefined_by
    )

    if np.isnan(expected):
        assert np.isnan(negative_likelihood_ratio)
    else:
        assert negative_likelihood_ratio == pytest.approx(expected)


def test_cohen_kappa():
    # These label vectors reproduce the contingency matrix from Artstein and
    # Poesio (2008), Table 1: np.array([[20, 20], [10, 50]]).
    y1 = np.array([0] * 40 + [1] * 60)
    y2 = np.array([0] * 20 + [1] * 20 + [0] * 10 + [1] * 50)
    kappa = cohen_kappa_score(y1, y2)
    assert_almost_equal(kappa, 0.348, decimal=3)
    assert kappa == cohen_kappa_score(y2, y1)

    # Add spurious labels and ignore them.
    y1 = np.append(y1, [2] * 4)
    y2 = np.append(y2, [2] * 4)
    assert cohen_kappa_score(y1, y2, labels=[0, 1]) == kappa

    assert_almost_equal(cohen_kappa_score(y1, y1), 1.0)

    # Multiclass example: Artstein and Poesio, Table 4.
    y1 = np.array([0] * 46 + [1] * 44 + [2] * 10)
    y2 = np.array([0] * 52 + [1] * 32 + [2] * 16)
    assert_almost_equal(cohen_kappa_score(y1, y2), 0.8013, decimal=4)

    # Weighting example: none, linear, quadratic.
    y1 = np.array([0] * 46 + [1] * 44 + [2] * 10)
    y2 = np.array([0] * 50 + [1] * 40 + [2] * 10)
    assert_almost_equal(cohen_kappa_score(y1, y2), 0.9315, decimal=4)
    assert_almost_equal(cohen_kappa_score(y1, y2, weights="linear"), 0.9412, decimal=4)
    assert_almost_equal(
        cohen_kappa_score(y1, y2, weights="quadratic"), 0.9541, decimal=4
    )


def test_cohen_kappa_score_error_wrong_label():
    """Test that correct error is raised when users pass labels that are not in y1."""
    labels = [1, 2]
    y1 = np.array(["a"] * 5 + ["b"] * 5)
    y2 = np.array(["b"] * 10)
    with pytest.raises(
        ValueError, match="At least one label in `labels` must be present in `y1`"
    ):
        cohen_kappa_score(y1, y2, labels=labels)


@pytest.mark.parametrize("zero_division", [0, 1, np.nan])
@pytest.mark.parametrize("y_true, y_pred", [([0], [0])])
@pytest.mark.parametrize(
    "metric",
    [
        f1_score,
        partial(fbeta_score, beta=1),
        precision_score,
        recall_score,
    ],
)
def test_zero_division_nan_no_warning(metric, y_true, y_pred, zero_division):
    """Check the behaviour of `zero_division` when setting to 0, 1 or np.nan.
    No warnings should be raised.
    """
    with warnings.catch_warnings():
        warnings.simplefilter("error")
        result = metric(y_true, y_pred, zero_division=zero_division)

    if np.isnan(zero_division):
        assert np.isnan(result)
    else:
        assert result == zero_division


@pytest.mark.parametrize("y_true, y_pred", [([0], [0])])
@pytest.mark.parametrize(
    "metric",
    [
        f1_score,
        partial(fbeta_score, beta=1),
        precision_score,
        recall_score,
    ],
)
def test_zero_division_nan_warning(metric, y_true, y_pred):
    """Check the behaviour of `zero_division` when setting to "warn".
    A `UndefinedMetricWarning` should be raised.
    """
    with pytest.warns(UndefinedMetricWarning):
        result = metric(y_true, y_pred, zero_division="warn")
    assert result == 0.0


def test_matthews_corrcoef_against_numpy_corrcoef(global_random_seed):
    rng = np.random.RandomState(global_random_seed)
    y_true = rng.randint(0, 2, size=20)
    y_pred = rng.randint(0, 2, size=20)

    assert_almost_equal(
        matthews_corrcoef(y_true, y_pred), np.corrcoef(y_true, y_pred)[0, 1], 10
    )


def test_matthews_corrcoef_against_jurman(global_random_seed):
    # Check that the multiclass matthews_corrcoef agrees with the definition
    # presented in Jurman, Riccadonna, Furlanello, (2012). A Comparison of MCC
    # and CEN Error Measures in MultiClass Prediction
    rng = np.random.RandomState(global_random_seed)
    y_true = rng.randint(0, 2, size=20)
    y_pred = rng.randint(0, 2, size=20)
    sample_weight = rng.rand(20)

    C = confusion_matrix(y_true, y_pred, sample_weight=sample_weight)
    N = len(C)
    cov_ytyp = sum(
        [
            C[k, k] * C[m, l] - C[l, k] * C[k, m]
            for k in range(N)
            for m in range(N)
            for l in range(N)
        ]
    )
    cov_ytyt = sum(
        [
            C[:, k].sum()
            * np.sum([C[g, f] for f in range(N) for g in range(N) if f != k])
            for k in range(N)
        ]
    )
    cov_ypyp = np.sum(
        [
            C[k, :].sum()
            * np.sum([C[f, g] for f in range(N) for g in range(N) if f != k])
            for k in range(N)
        ]
    )
    mcc_jurman = cov_ytyp / np.sqrt(cov_ytyt * cov_ypyp)
    mcc_ours = matthews_corrcoef(y_true, y_pred, sample_weight=sample_weight)

    assert_almost_equal(mcc_ours, mcc_jurman, 10)


def test_matthews_corrcoef(global_random_seed):
    rng = np.random.RandomState(global_random_seed)
    y_true = ["a" if i == 0 else "b" for i in rng.randint(0, 2, size=20)]

    # corrcoef of same vectors must be 1
    assert_almost_equal(matthews_corrcoef(y_true, y_true), 1.0)

    # corrcoef, when the two vectors are opposites of each other, should be -1
    y_true_inv = ["b" if i == "a" else "a" for i in y_true]
    assert_almost_equal(matthews_corrcoef(y_true, y_true_inv), -1)

    y_true_inv2 = label_binarize(y_true, classes=["a", "b"])
    y_true_inv2 = np.where(y_true_inv2, "a", "b")
    assert_almost_equal(matthews_corrcoef(y_true, y_true_inv2), -1)

    # For the zero vector case, the corrcoef cannot be calculated and should
    # output 0
    assert_almost_equal(matthews_corrcoef([0, 0, 0, 0], [0, 0, 0, 0]), 0.0)

    # And also for any other vector with 0 variance
    assert_almost_equal(matthews_corrcoef(y_true, ["a"] * len(y_true)), 0.0)

    # These two vectors have 0 correlation and hence mcc should be 0
    y_1 = [1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1]
    y_2 = [1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1]
    assert_almost_equal(matthews_corrcoef(y_1, y_2), 0.0)

    # Check that sample weight is able to selectively exclude
    mask = [1] * 10 + [0] * 10
    # Now the first half of the vector elements are alone given a weight of 1
    # and hence the mcc will not be a perfect 0 as in the previous case
    with pytest.raises(AssertionError):
        assert_almost_equal(matthews_corrcoef(y_1, y_2, sample_weight=mask), 0.0)


def test_matthews_corrcoef_multiclass(global_random_seed):
    rng = np.random.RandomState(global_random_seed)
    ord_a = ord("a")
    n_classes = 4
    y_true = [chr(ord_a + i) for i in rng.randint(0, n_classes, size=20)]

    # corrcoef of same vectors must be 1
    assert_almost_equal(matthews_corrcoef(y_true, y_true), 1.0)

    # with multiclass > 2 it is not possible to achieve -1
    y_true = [0, 0, 1, 1, 2, 2]
    y_pred_bad = [2, 2, 0, 0, 1, 1]
    assert_almost_equal(matthews_corrcoef(y_true, y_pred_bad), -0.5)

    # Maximizing false positives and negatives minimizes the MCC
    # The minimum will be different for depending on the input
    y_true = [0, 0, 1, 1, 2, 2]
    y_pred_min = [1, 1, 0, 0, 0, 0]
    assert_almost_equal(matthews_corrcoef(y_true, y_pred_min), -12 / np.sqrt(24 * 16))

    # Zero variance will result in an mcc of zero
    y_true = [0, 1, 2]
    y_pred = [3, 3, 3]
    assert_almost_equal(matthews_corrcoef(y_true, y_pred), 0.0)

    # Also for ground truth with zero variance
    y_true = [3, 3, 3]
    y_pred = [0, 1, 2]
    assert_almost_equal(matthews_corrcoef(y_true, y_pred), 0.0)

    # These two vectors have 0 correlation and hence mcc should be 0
    y_1 = [0, 1, 2, 0, 1, 2, 0, 1, 2]
    y_2 = [1, 1, 1, 2, 2, 2, 0, 0, 0]
    assert_almost_equal(matthews_corrcoef(y_1, y_2), 0.0)

    # We can test that binary assumptions hold using the multiclass computation
    # by masking the weight of samples not in the first two classes

    # Masking the last label should let us get an MCC of -1
    y_true = [0, 0, 1, 1, 2]
    y_pred = [1, 1, 0, 0, 2]
    sample_weight = [1, 1, 1, 1, 0]
    assert_almost_equal(
        matthews_corrcoef(y_true, y_pred, sample_weight=sample_weight), -1
    )

    # For the zero vector case, the corrcoef cannot be calculated and should
    # output 0
    y_true = [0, 0, 1, 2]
    y_pred = [0, 0, 1, 2]
    sample_weight = [1, 1, 0, 0]
    assert_almost_equal(
        matthews_corrcoef(y_true, y_pred, sample_weight=sample_weight), 0.0
    )


@pytest.mark.parametrize("n_points", [100, 10000])
def test_matthews_corrcoef_overflow(n_points, global_random_seed):
    # https://github.com/scikit-learn/scikit-learn/issues/9622
    rng = np.random.RandomState(global_random_seed)

    def mcc_safe(y_true, y_pred):
        conf_matrix = confusion_matrix(y_true, y_pred)
        true_pos = conf_matrix[1, 1]
        false_pos = conf_matrix[1, 0]
        false_neg = conf_matrix[0, 1]
        n_points = len(y_true)
        pos_rate = (true_pos + false_neg) / n_points
        activity = (true_pos + false_pos) / n_points
        mcc_numerator = true_pos / n_points - pos_rate * activity
        mcc_denominator = activity * pos_rate * (1 - activity) * (1 - pos_rate)
        return mcc_numerator / np.sqrt(mcc_denominator)

    def random_ys(n_points):  # binary
        x_true = rng.random_sample(n_points)
        x_pred = x_true + 0.2 * (rng.random_sample(n_points) - 0.5)
        y_true = x_true > 0.5
        y_pred = x_pred > 0.5
        return y_true, y_pred

    arr = np.repeat([0.0, 1.0], n_points)  # binary
    assert_almost_equal(matthews_corrcoef(arr, arr), 1.0)
    arr = np.repeat([0.0, 1.0, 2.0], n_points)  # multiclass
    assert_almost_equal(matthews_corrcoef(arr, arr), 1.0)

    y_true, y_pred = random_ys(n_points)
    assert_almost_equal(matthews_corrcoef(y_true, y_true), 1.0)
    assert_almost_equal(matthews_corrcoef(y_true, y_pred), mcc_safe(y_true, y_pred))


def test_precision_recall_f1_score_multiclass():
    # Test Precision Recall and F1 Score for multiclass classification task
    y_true, y_pred, _ = make_prediction(binary=False)

    # compute scores with default labels introspection
    p, r, f, s = precision_recall_fscore_support(y_true, y_pred, average=None)
    assert_array_almost_equal(p, [0.83, 0.33, 0.42], 2)
    assert_array_almost_equal(r, [0.79, 0.09, 0.90], 2)
    assert_array_almost_equal(f, [0.81, 0.15, 0.57], 2)
    assert_array_equal(s, [24, 31, 20])

    # averaging tests
    ps = precision_score(y_true, y_pred, pos_label=1, average="micro")
    assert_array_almost_equal(ps, 0.53, 2)

    rs = recall_score(y_true, y_pred, average="micro")
    assert_array_almost_equal(rs, 0.53, 2)

    fs = f1_score(y_true, y_pred, average="micro")
    assert_array_almost_equal(fs, 0.53, 2)

    ps = precision_score(y_true, y_pred, average="macro")
    assert_array_almost_equal(ps, 0.53, 2)

    rs = recall_score(y_true, y_pred, average="macro")
    assert_array_almost_equal(rs, 0.60, 2)

    fs = f1_score(y_true, y_pred, average="macro")
    assert_array_almost_equal(fs, 0.51, 2)

    ps = precision_score(y_true, y_pred, average="weighted")
    assert_array_almost_equal(ps, 0.51, 2)

    rs = recall_score(y_true, y_pred, average="weighted")
    assert_array_almost_equal(rs, 0.53, 2)

    fs = f1_score(y_true, y_pred, average="weighted")
    assert_array_almost_equal(fs, 0.47, 2)

    with pytest.raises(ValueError):
        precision_score(y_true, y_pred, average="samples")
    with pytest.raises(ValueError):
        recall_score(y_true, y_pred, average="samples")
    with pytest.raises(ValueError):
        f1_score(y_true, y_pred, average="samples")
    with pytest.raises(ValueError):
        fbeta_score(y_true, y_pred, average="samples", beta=0.5)

    # same prediction but with and explicit label ordering
    p, r, f, s = precision_recall_fscore_support(
        y_true, y_pred, labels=[0, 2, 1], average=None
    )
    assert_array_almost_equal(p, [0.83, 0.41, 0.33], 2)
    assert_array_almost_equal(r, [0.79, 0.90, 0.10], 2)
    assert_array_almost_equal(f, [0.81, 0.57, 0.15], 2)
    assert_array_equal(s, [24, 20, 31])


@pytest.mark.parametrize("average", ["samples", "micro", "macro", "weighted", None])
def test_precision_refcall_f1_score_multilabel_unordered_labels(average):
    # test that labels need not be sorted in the multilabel case
    y_true = np.array([[1, 1, 0, 0]])
    y_pred = np.array([[0, 0, 1, 1]])
    p, r, f, s = precision_recall_fscore_support(
        y_true, y_pred, labels=[3, 0, 1, 2], warn_for=[], average=average
    )
    assert_array_equal(p, 0)
    assert_array_equal(r, 0)
    assert_array_equal(f, 0)
    if average is None:
        assert_array_equal(s, [0, 1, 1, 0])


def test_precision_recall_f1_score_binary_averaged():
    y_true = np.array([0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 0, 1, 0, 1])
    y_pred = np.array([1, 1, 0, 1, 0, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1])

    # compute scores with default labels introspection
    ps, rs, fs, _ = precision_recall_fscore_support(y_true, y_pred, average=None)
    p, r, f, _ = precision_recall_fscore_support(y_true, y_pred, average="macro")
    assert p == np.mean(ps)
    assert r == np.mean(rs)
    assert f == np.mean(fs)
    p, r, f, _ = precision_recall_fscore_support(y_true, y_pred, average="weighted")
    support = np.bincount(y_true)
    assert p == np.average(ps, weights=support)
    assert r == np.average(rs, weights=support)
    assert f == np.average(fs, weights=support)


def test_zero_precision_recall():
    # Check that pathological cases do not bring NaNs

    old_error_settings = np.seterr(all="raise")

    try:
        y_true = np.array([0, 1, 2, 0, 1, 2])
        y_pred = np.array([2, 0, 1, 1, 2, 0])

        assert_almost_equal(precision_score(y_true, y_pred, average="macro"), 0.0, 2)
        assert_almost_equal(recall_score(y_true, y_pred, average="macro"), 0.0, 2)
        assert_almost_equal(f1_score(y_true, y_pred, average="macro"), 0.0, 2)

    finally:
        np.seterr(**old_error_settings)


def test_confusion_matrix_multiclass_subset_labels():
    # Test confusion matrix - multi-class case with subset of labels
    y_true, y_pred, _ = make_prediction(binary=False)

    # compute confusion matrix with only first two labels considered
    cm = confusion_matrix(y_true, y_pred, labels=[0, 1])
    assert_array_equal(cm, [[19, 4], [4, 3]])

    # compute confusion matrix with explicit label ordering for only subset
    # of labels
    cm = confusion_matrix(y_true, y_pred, labels=[2, 1])
    assert_array_equal(cm, [[18, 2], [24, 3]])

    # a label not in y_true should result in zeros for that row/column
    extra_label = np.max(y_true) + 1
    cm = confusion_matrix(y_true, y_pred, labels=[2, extra_label])
    assert_array_equal(cm, [[18, 0], [0, 0]])


@pytest.mark.parametrize(
    "labels, err_msg",
    [
        ([], "'labels' should contains at least one label."),
        ([3, 4], "At least one label specified must be in y_true"),
    ],
    ids=["empty list", "unknown labels"],
)
def test_confusion_matrix_error(labels, err_msg):
    y_true, y_pred, _ = make_prediction(binary=False)
    with pytest.raises(ValueError, match=err_msg):
        confusion_matrix(y_true, y_pred, labels=labels)


@pytest.mark.parametrize(
    "labels", (None, [0, 1], [0, 1, 2]), ids=["None", "binary", "multiclass"]
)
def test_confusion_matrix_on_zero_length_input(labels):
    expected_n_classes = len(labels) if labels else 0
    expected = np.zeros((expected_n_classes, expected_n_classes), dtype=int)
    cm = confusion_matrix([], [], labels=labels)
    assert_array_equal(cm, expected)


def test_confusion_matrix_dtype():
    y = [0, 1, 1]
    weight = np.ones(len(y))
    # confusion_matrix returns int64 by default
    cm = confusion_matrix(y, y)
    assert cm.dtype == np.int64
    # The dtype of confusion_matrix is always 64 bit
    for dtype in [np.bool_, np.int32, np.uint64]:
        cm = confusion_matrix(y, y, sample_weight=weight.astype(dtype, copy=False))
        assert cm.dtype == np.int64
    for dtype in [np.float32, np.float64, None, object]:
        cm = confusion_matrix(y, y, sample_weight=weight.astype(dtype, copy=False))
        assert cm.dtype == np.float64

    # np.iinfo(np.uint32).max should be accumulated correctly
    weight = np.full(len(y), 4294967295, dtype=np.uint32)
    cm = confusion_matrix(y, y, sample_weight=weight)
    assert cm[0, 0] == 4294967295
    assert cm[1, 1] == 8589934590

    # np.iinfo(np.int64).max should cause an overflow
    weight = np.full(len(y), 9223372036854775807, dtype=np.int64)
    cm = confusion_matrix(y, y, sample_weight=weight)
    assert cm[0, 0] == 9223372036854775807
    assert cm[1, 1] == -2


@pytest.mark.parametrize("dtype", ["Int64", "Float64", "boolean"])
def test_confusion_matrix_pandas_nullable(dtype):
    """Checks that confusion_matrix works with pandas nullable dtypes.

    Non-regression test for gh-25635.
    """
    pd = pytest.importorskip("pandas")

    y_ndarray = np.array([1, 0, 0, 1, 0, 1, 1, 0, 1])
    y_true = pd.Series(y_ndarray, dtype=dtype)
    y_predicted = pd.Series([0, 0, 1, 1, 0, 1, 1, 1, 1], dtype="int64")

    output = confusion_matrix(y_true, y_predicted)
    expected_output = confusion_matrix(y_ndarray, y_predicted)

    assert_array_equal(output, expected_output)


def test_classification_report_multiclass():
    # Test performance report
    iris = datasets.load_iris()
    y_true, y_pred, _ = make_prediction(dataset=iris, binary=False)

    # print classification report with class names
    expected_report = """\
              precision    recall  f1-score   support

      setosa       0.83      0.79      0.81        24
  versicolor       0.33      0.10      0.15        31
   virginica       0.42      0.90      0.57        20

    accuracy                           0.53        75
   macro avg       0.53      0.60      0.51        75
weighted avg       0.51      0.53      0.47        75
"""
    report = classification_report(
        y_true,
        y_pred,
        labels=np.arange(len(iris.target_names)),
        target_names=iris.target_names,
    )
    assert report == expected_report


def test_classification_report_multiclass_balanced():
    y_true, y_pred = [0, 0, 0, 1, 1, 1, 2, 2, 2], [0, 1, 2, 0, 1, 2, 0, 1, 2]

    expected_report = """\
              precision    recall  f1-score   support

           0       0.33      0.33      0.33         3
           1       0.33      0.33      0.33         3
           2       0.33      0.33      0.33         3

    accuracy                           0.33         9
   macro avg       0.33      0.33      0.33         9
weighted avg       0.33      0.33      0.33         9
"""
    report = classification_report(y_true, y_pred)
    assert report == expected_report


def test_classification_report_multiclass_with_label_detection():
    iris = datasets.load_iris()
    y_true, y_pred, _ = make_prediction(dataset=iris, binary=False)

    # print classification report with label detection
    expected_report = """\
              precision    recall  f1-score   support

           0       0.83      0.79      0.81        24
           1       0.33      0.10      0.15        31
           2       0.42      0.90      0.57        20

    accuracy                           0.53        75
   macro avg       0.53      0.60      0.51        75
weighted avg       0.51      0.53      0.47        75
"""
    report = classification_report(y_true, y_pred)
    assert report == expected_report


def test_classification_report_multiclass_with_digits():
    # Test performance report with added digits in floating point values
    iris = datasets.load_iris()
    y_true, y_pred, _ = make_prediction(dataset=iris, binary=False)

    # print classification report with class names
    expected_report = """\
              precision    recall  f1-score   support

      setosa    0.82609   0.79167   0.80851        24
  versicolor    0.33333   0.09677   0.15000        31
   virginica    0.41860   0.90000   0.57143        20

    accuracy                        0.53333        75
   macro avg    0.52601   0.59615   0.50998        75
weighted avg    0.51375   0.53333   0.47310        75
"""
    report = classification_report(
        y_true,
        y_pred,
        labels=np.arange(len(iris.target_names)),
        target_names=iris.target_names,
        digits=5,
    )
    assert report == expected_report


def test_classification_report_multiclass_with_string_label():
    y_true, y_pred, _ = make_prediction(binary=False)

    y_true = np.array(["blue", "green", "red"])[y_true]
    y_pred = np.array(["blue", "green", "red"])[y_pred]

    expected_report = """\
              precision    recall  f1-score   support

        blue       0.83      0.79      0.81        24
       green       0.33      0.10      0.15        31
         red       0.42      0.90      0.57        20

    accuracy                           0.53        75
   macro avg       0.53      0.60      0.51        75
weighted avg       0.51      0.53      0.47        75
"""
    report = classification_report(y_true, y_pred)
    assert report == expected_report

    expected_report = """\
              precision    recall  f1-score   support

           a       0.83      0.79      0.81        24
           b       0.33      0.10      0.15        31
           c       0.42      0.90      0.57        20

    accuracy                           0.53        75
   macro avg       0.53      0.60      0.51        75
weighted avg       0.51      0.53      0.47        75
"""
    report = classification_report(y_true, y_pred, target_names=["a", "b", "c"])
    assert report == expected_report


def test_classification_report_multiclass_with_unicode_label():
    y_true, y_pred, _ = make_prediction(binary=False)

    labels = np.array(["blue\xa2", "green\xa2", "red\xa2"])
    y_true = labels[y_true]
    y_pred = labels[y_pred]

    expected_report = """\
              precision    recall  f1-score   support

       blue\xa2       0.83      0.79      0.81        24
      green\xa2       0.33      0.10      0.15        31
        red\xa2       0.42      0.90      0.57        20

    accuracy                           0.53        75
   macro avg       0.53      0.60      0.51        75
weighted avg       0.51      0.53      0.47        75
"""
    report = classification_report(y_true, y_pred)
    assert report == expected_report


def test_classification_report_multiclass_with_long_string_label():
    y_true, y_pred, _ = make_prediction(binary=False)

    labels = np.array(["blue", "green" * 5, "red"])
    y_true = labels[y_true]
    y_pred = labels[y_pred]

    expected_report = """\
                           precision    recall  f1-score   support

                     blue       0.83      0.79      0.81        24
greengreengreengreengreen       0.33      0.10      0.15        31
                      red       0.42      0.90      0.57        20

                 accuracy                           0.53        75
                macro avg       0.53      0.60      0.51        75
             weighted avg       0.51      0.53      0.47        75
"""

    report = classification_report(y_true, y_pred)
    assert report == expected_report


def test_classification_report_labels_target_names_unequal_length():
    y_true = [0, 0, 2, 0, 0]
    y_pred = [0, 2, 2, 0, 0]
    target_names = ["class 0", "class 1", "class 2"]

    msg = "labels size, 2, does not match size of target_names, 3"
    with pytest.warns(UserWarning, match=msg):
        classification_report(y_true, y_pred, labels=[0, 2], target_names=target_names)


def test_classification_report_no_labels_target_names_unequal_length():
    y_true = [0, 0, 2, 0, 0]
    y_pred = [0, 2, 2, 0, 0]
    target_names = ["class 0", "class 1", "class 2"]

    err_msg = (
        "Number of classes, 2, does not "
        "match size of target_names, 3. "
        "Try specifying the labels parameter"
    )
    with pytest.raises(ValueError, match=err_msg):
        classification_report(y_true, y_pred, target_names=target_names)


@pytest.mark.filterwarnings(r"ignore::sklearn.exceptions.UndefinedMetricWarning")
def test_multilabel_classification_report():
    n_classes = 4
    n_samples = 50

    _, y_true = make_multilabel_classification(
        n_features=1, n_samples=n_samples, n_classes=n_classes, random_state=0
    )

    _, y_pred = make_multilabel_classification(
        n_features=1, n_samples=n_samples, n_classes=n_classes, random_state=1
    )

    expected_report = """\
              precision    recall  f1-score   support

           0       0.50      0.67      0.57        24
           1       0.51      0.74      0.61        27
           2       0.29      0.08      0.12        26
           3       0.52      0.56      0.54        27

   micro avg       0.50      0.51      0.50       104
   macro avg       0.45      0.51      0.46       104
weighted avg       0.45      0.51      0.46       104
 samples avg       0.46      0.42      0.40       104
"""

    report = classification_report(y_true, y_pred)
    assert report == expected_report


def test_multilabel_zero_one_loss_subset():
    # Dense label indicator matrix format
    y1 = np.array([[0, 1, 1], [1, 0, 1]])
    y2 = np.array([[0, 0, 1], [1, 0, 1]])

    assert zero_one_loss(y1, y2) == 0.5
    assert zero_one_loss(y1, y1) == 0
    assert zero_one_loss(y2, y2) == 0
    assert zero_one_loss(y2, np.logical_not(y2)) == 1
    assert zero_one_loss(y1, np.logical_not(y1)) == 1
    assert zero_one_loss(y1, np.zeros(y1.shape)) == 1
    assert zero_one_loss(y2, np.zeros(y1.shape)) == 1


def test_multilabel_hamming_loss():
    # Dense label indicator matrix format
    y1 = np.array([[0, 1, 1], [1, 0, 1]])
    y2 = np.array([[0, 0, 1], [1, 0, 1]])
    w = np.array([1, 3])

    assert hamming_loss(y1, y2) == 1 / 6
    assert hamming_loss(y1, y1) == 0
    assert hamming_loss(y2, y2) == 0
    assert hamming_loss(y2, 1 - y2) == 1
    assert hamming_loss(y1, 1 - y1) == 1
    assert hamming_loss(y1, np.zeros(y1.shape)) == 4 / 6
    assert hamming_loss(y2, np.zeros(y1.shape)) == 0.5
    assert hamming_loss(y1, y2, sample_weight=w) == 1.0 / 12
    assert hamming_loss(y1, 1 - y2, sample_weight=w) == 11.0 / 12
    assert hamming_loss(y1, np.zeros_like(y1), sample_weight=w) == 2.0 / 3
    # sp_hamming only works with 1-D arrays
    assert hamming_loss(y1[0], y2[0]) == sp_hamming(y1[0], y2[0])


def test_jaccard_score_validation():
    y_true = np.array([0, 1, 0, 1, 1])
    y_pred = np.array([0, 1, 0, 1, 1])
    err_msg = r"pos_label=2 is not a valid label. It should be one of \[0, 1\]"
    with pytest.raises(ValueError, match=err_msg):
        jaccard_score(y_true, y_pred, average="binary", pos_label=2)

    y_true = np.array([[0, 1, 1], [1, 0, 0]])
    y_pred = np.array([[1, 1, 1], [1, 0, 1]])
    msg1 = (
        r"Target is multilabel-indicator but average='binary'. "
        r"Please choose another average setting, one of \[None, "
        r"'micro', 'macro', 'weighted', 'samples'\]."
    )
    with pytest.raises(ValueError, match=msg1):
        jaccard_score(y_true, y_pred, average="binary", pos_label=-1)

    y_true = np.array([0, 1, 1, 0, 2])
    y_pred = np.array([1, 1, 1, 1, 0])
    msg2 = (
        r"Target is multiclass but average='binary'. Please choose "
        r"another average setting, one of \[None, 'micro', 'macro', "
        r"'weighted'\]."
    )
    with pytest.raises(ValueError, match=msg2):
        jaccard_score(y_true, y_pred, average="binary")
    msg3 = "Samplewise metrics are not available outside of multilabel classification."
    with pytest.raises(ValueError, match=msg3):
        jaccard_score(y_true, y_pred, average="samples")

    msg = (
        r"Note that pos_label \(set to 3\) is ignored when "
        r"average != 'binary' \(got 'micro'\). You may use "
        r"labels=\[pos_label\] to specify a single positive "
        "class."
    )
    with pytest.warns(UserWarning, match=msg):
        jaccard_score(y_true, y_pred, average="micro", pos_label=3)


def test_multilabel_jaccard_score(recwarn):
    # Dense label indicator matrix format
    y1 = np.array([[0, 1, 1], [1, 0, 1]])
    y2 = np.array([[0, 0, 1], [1, 0, 1]])

    # size(y1 \inter y2) = [1, 2]
    # size(y1 \union y2) = [2, 2]

    assert jaccard_score(y1, y2, average="samples") == 0.75
    assert jaccard_score(y1, y1, average="samples") == 1
    assert jaccard_score(y2, y2, average="samples") == 1
    assert jaccard_score(y2, np.logical_not(y2), average="samples") == 0
    assert jaccard_score(y1, np.logical_not(y1), average="samples") == 0
    assert jaccard_score(y1, np.zeros(y1.shape), average="samples") == 0
    assert jaccard_score(y2, np.zeros(y1.shape), average="samples") == 0

    y_true = np.array([[0, 1, 1], [1, 0, 0]])
    y_pred = np.array([[1, 1, 1], [1, 0, 1]])
    # average='macro'
    assert_almost_equal(jaccard_score(y_true, y_pred, average="macro"), 2.0 / 3)
    # average='micro'
    assert_almost_equal(jaccard_score(y_true, y_pred, average="micro"), 3.0 / 5)
    # average='samples'
    assert_almost_equal(jaccard_score(y_true, y_pred, average="samples"), 7.0 / 12)
    assert_almost_equal(
        jaccard_score(y_true, y_pred, average="samples", labels=[0, 2]), 1.0 / 2
    )
    assert_almost_equal(
        jaccard_score(y_true, y_pred, average="samples", labels=[1, 2]), 1.0 / 2
    )
    # average=None
    assert_array_equal(
        jaccard_score(y_true, y_pred, average=None), np.array([1.0 / 2, 1.0, 1.0 / 2])
    )

    y_true = np.array([[0, 1, 1], [1, 0, 1]])
    y_pred = np.array([[1, 1, 1], [1, 0, 1]])
    assert_almost_equal(jaccard_score(y_true, y_pred, average="macro"), 5.0 / 6)
    # average='weighted'
    assert_almost_equal(jaccard_score(y_true, y_pred, average="weighted"), 7.0 / 8)

    msg2 = "Got 4 > 2"
    with pytest.raises(ValueError, match=msg2):
        jaccard_score(y_true, y_pred, labels=[4], average="macro")
    msg3 = "Got -1 < 0"
    with pytest.raises(ValueError, match=msg3):
        jaccard_score(y_true, y_pred, labels=[-1], average="macro")

    msg = (
        "Jaccard is ill-defined and being set to 0.0 in labels "
        "with no true or predicted samples."
    )

    with pytest.warns(UndefinedMetricWarning, match=msg):
        assert (
            jaccard_score(np.array([[0, 1]]), np.array([[0, 1]]), average="macro")
            == 0.5
        )

    msg = (
        "Jaccard is ill-defined and being set to 0.0 in samples "
        "with no true or predicted labels."
    )

    with pytest.warns(UndefinedMetricWarning, match=msg):
        assert (
            jaccard_score(
                np.array([[0, 0], [1, 1]]),
                np.array([[0, 0], [1, 1]]),
                average="samples",
            )
            == 0.5
        )

    assert not list(recwarn)


def test_multiclass_jaccard_score(recwarn):
    y_true = ["ant", "ant", "cat", "cat", "ant", "cat", "bird", "bird"]
    y_pred = ["cat", "ant", "cat", "cat", "ant", "bird", "bird", "cat"]
    labels = ["ant", "bird", "cat"]
    lb = LabelBinarizer()
    lb.fit(labels)
    y_true_bin = lb.transform(y_true)
    y_pred_bin = lb.transform(y_pred)
    multi_jaccard_score = partial(jaccard_score, y_true, y_pred)
    bin_jaccard_score = partial(jaccard_score, y_true_bin, y_pred_bin)
    multi_labels_list = [
        ["ant", "bird"],
        ["ant", "cat"],
        ["cat", "bird"],
        ["ant"],
        ["bird"],
        ["cat"],
        None,
    ]
    bin_labels_list = [[0, 1], [0, 2], [2, 1], [0], [1], [2], None]

    # other than average='samples'/'none-samples', test everything else here
    for average in ("macro", "weighted", "micro", None):
        for m_label, b_label in zip(multi_labels_list, bin_labels_list):
            assert_almost_equal(
                multi_jaccard_score(average=average, labels=m_label),
                bin_jaccard_score(average=average, labels=b_label),
            )

    y_true = np.array([[0, 0], [0, 0], [0, 0]])
    y_pred = np.array([[0, 0], [0, 0], [0, 0]])
    with ignore_warnings():
        assert jaccard_score(y_true, y_pred, average="weighted") == 0

    assert not list(recwarn)


def test_average_binary_jaccard_score(recwarn):
    # tp=0, fp=0, fn=1, tn=0
    assert jaccard_score([1], [0], average="binary") == 0.0
    # tp=0, fp=0, fn=0, tn=1
    msg = (
        "Jaccard is ill-defined and being set to 0.0 due to "
        "no true or predicted samples"
    )
    with pytest.warns(UndefinedMetricWarning, match=msg):
        assert jaccard_score([0, 0], [0, 0], average="binary") == 0.0

    # tp=1, fp=0, fn=0, tn=0 (pos_label=0)
    assert jaccard_score([0], [0], pos_label=0, average="binary") == 1.0
    y_true = np.array([1, 0, 1, 1, 0])
    y_pred = np.array([1, 0, 1, 1, 1])
    assert_almost_equal(jaccard_score(y_true, y_pred, average="binary"), 3.0 / 4)
    assert_almost_equal(
        jaccard_score(y_true, y_pred, average="binary", pos_label=0), 1.0 / 2
    )

    assert not list(recwarn)


def test_jaccard_score_zero_division_warning():
    # check that we raised a warning with default behavior if a zero division
    # happens
    y_true = np.array([[1, 0, 1], [0, 0, 0]])
    y_pred = np.array([[0, 0, 0], [0, 0, 0]])
    msg = (
        "Jaccard is ill-defined and being set to 0.0 in "
        "samples with no true or predicted labels."
        " Use `zero_division` parameter to control this behavior."
    )
    with pytest.warns(UndefinedMetricWarning, match=msg):
        score = jaccard_score(y_true, y_pred, average="samples", zero_division="warn")
        assert score == pytest.approx(0.0)


@pytest.mark.parametrize("zero_division, expected_score", [(0, 0), (1, 0.5)])
def test_jaccard_score_zero_division_set_value(zero_division, expected_score):
    # check that we don't issue warning by passing the zero_division parameter
    y_true = np.array([[1, 0, 1], [0, 0, 0]])
    y_pred = np.array([[0, 0, 0], [0, 0, 0]])
    with warnings.catch_warnings():
        warnings.simplefilter("error", UndefinedMetricWarning)
        score = jaccard_score(
            y_true, y_pred, average="samples", zero_division=zero_division
        )
    assert score == pytest.approx(expected_score)


@pytest.mark.filterwarnings(r"ignore::sklearn.exceptions.UndefinedMetricWarning")
def test_precision_recall_f1_score_multilabel_1():
    # Test precision_recall_f1_score on a crafted multilabel example
    # First crafted example

    y_true = np.array([[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 1, 1]])
    y_pred = np.array([[0, 1, 0, 0], [0, 1, 0, 0], [1, 0, 1, 0]])

    p, r, f, s = precision_recall_fscore_support(y_true, y_pred, average=None)

    # tp = [0, 1, 1, 0]
    # fn = [1, 0, 0, 1]
    # fp = [1, 1, 0, 0]
    # Check per class

    assert_array_almost_equal(p, [0.0, 0.5, 1.0, 0.0], 2)
    assert_array_almost_equal(r, [0.0, 1.0, 1.0, 0.0], 2)
    assert_array_almost_equal(f, [0.0, 1 / 1.5, 1, 0.0], 2)
    assert_array_almost_equal(s, [1, 1, 1, 1], 2)

    f2 = fbeta_score(y_true, y_pred, beta=2, average=None)
    support = s
    assert_array_almost_equal(f2, [0, 0.83, 1, 0], 2)

    # Check macro
    p, r, f, s = precision_recall_fscore_support(y_true, y_pred, average="macro")
    assert_almost_equal(p, 1.5 / 4)
    assert_almost_equal(r, 0.5)
    assert_almost_equal(f, 2.5 / 1.5 * 0.25)
    assert s is None
    assert_almost_equal(
        fbeta_score(y_true, y_pred, beta=2, average="macro"), np.mean(f2)
    )

    # Check micro
    p, r, f, s = precision_recall_fscore_support(y_true, y_pred, average="micro")
    assert_almost_equal(p, 0.5)
    assert_almost_equal(r, 0.5)
    assert_almost_equal(f, 0.5)
    assert s is None
    assert_almost_equal(
        fbeta_score(y_true, y_pred, beta=2, average="micro"),
        (1 + 4) * p * r / (4 * p + r),
    )

    # Check weighted
    p, r, f, s = precision_recall_fscore_support(y_true, y_pred, average="weighted")
    assert_almost_equal(p, 1.5 / 4)
    assert_almost_equal(r, 0.5)
    assert_almost_equal(f, 2.5 / 1.5 * 0.25)
    assert s is None
    assert_almost_equal(
        fbeta_score(y_true, y_pred, beta=2, average="weighted"),
        np.average(f2, weights=support),
    )
    # Check samples
    # |h(x_i) inter y_i | = [0, 1, 1]
    # |y_i| = [1, 1, 2]
    # |h(x_i)| = [1, 1, 2]
    p, r, f, s = precision_recall_fscore_support(y_true, y_pred, average="samples")
    assert_almost_equal(p, 0.5)
    assert_almost_equal(r, 0.5)
    assert_almost_equal(f, 0.5)
    assert s is None
    assert_almost_equal(fbeta_score(y_true, y_pred, beta=2, average="samples"), 0.5)


@pytest.mark.filterwarnings(r"ignore::sklearn.exceptions.UndefinedMetricWarning")
def test_precision_recall_f1_score_multilabel_2():
    # Test precision_recall_f1_score on a crafted multilabel example 2
    # Second crafted example
    y_true = np.array([[1, 0, 0, 0], [0, 1, 0, 0], [0, 1, 1, 0]])
    y_pred = np.array([[0, 0, 0, 1], [0, 0, 0, 1], [1, 1, 0, 0]])

    # tp = [ 0.  1.  0.  0.]
    # fp = [ 1.  0.  0.  2.]
    # fn = [ 1.  1.  1.  0.]

    p, r, f, s = precision_recall_fscore_support(y_true, y_pred, average=None)
    assert_array_almost_equal(p, [0.0, 1.0, 0.0, 0.0], 2)
    assert_array_almost_equal(r, [0.0, 0.5, 0.0, 0.0], 2)
    assert_array_almost_equal(f, [0.0, 0.66, 0.0, 0.0], 2)
    assert_array_almost_equal(s, [1, 2, 1, 0], 2)

    f2 = fbeta_score(y_true, y_pred, beta=2, average=None)
    support = s
    assert_array_almost_equal(f2, [0, 0.55, 0, 0], 2)

    p, r, f, s = precision_recall_fscore_support(y_true, y_pred, average="micro")
    assert_almost_equal(p, 0.25)
    assert_almost_equal(r, 0.25)
    assert_almost_equal(f, 2 * 0.25 * 0.25 / 0.5)
    assert s is None
    assert_almost_equal(
        fbeta_score(y_true, y_pred, beta=2, average="micro"),
        (1 + 4) * p * r / (4 * p + r),
    )

    p, r, f, s = precision_recall_fscore_support(y_true, y_pred, average="macro")
    assert_almost_equal(p, 0.25)
    assert_almost_equal(r, 0.125)
    assert_almost_equal(f, 2 / 12)
    assert s is None
    assert_almost_equal(
        fbeta_score(y_true, y_pred, beta=2, average="macro"), np.mean(f2)
    )

    p, r, f, s = precision_recall_fscore_support(y_true, y_pred, average="weighted")
    assert_almost_equal(p, 2 / 4)
    assert_almost_equal(r, 1 / 4)
    assert_almost_equal(f, 2 / 3 * 2 / 4)
    assert s is None
    assert_almost_equal(
        fbeta_score(y_true, y_pred, beta=2, average="weighted"),
        np.average(f2, weights=support),
    )

    p, r, f, s = precision_recall_fscore_support(y_true, y_pred, average="samples")
    # Check samples
    # |h(x_i) inter y_i | = [0, 0, 1]
    # |y_i| = [1, 1, 2]
    # |h(x_i)| = [1, 1, 2]

    assert_almost_equal(p, 1 / 6)
    assert_almost_equal(r, 1 / 6)
    assert_almost_equal(f, 2 / 4 * 1 / 3)
    assert s is None
    assert_almost_equal(
        fbeta_score(y_true, y_pred, beta=2, average="samples"), 0.1666, 2
    )


@pytest.mark.filterwarnings(r"ignore::sklearn.exceptions.UndefinedMetricWarning")
@pytest.mark.parametrize(
    "zero_division, zero_division_expected",
    [("warn", 0), (0, 0), (1, 1), (np.nan, np.nan)],
)
def test_precision_recall_f1_score_with_an_empty_prediction(
    zero_division, zero_division_expected
):
    y_true = np.array([[0, 1, 0, 0], [1, 0, 0, 0], [0, 1, 1, 0]])
    y_pred = np.array([[0, 0, 0, 0], [0, 0, 0, 1], [0, 1, 1, 0]])

    # true_pos = [ 0.  1.  1.  0.]
    # false_pos = [ 0.  0.  0.  1.]
    # false_neg = [ 1.  1.  0.  0.]

    p, r, f, s = precision_recall_fscore_support(
        y_true, y_pred, average=None, zero_division=zero_division
    )

    assert_array_almost_equal(p, [zero_division_expected, 1.0, 1.0, 0.0], 2)
    assert_array_almost_equal(r, [0.0, 0.5, 1.0, zero_division_expected], 2)
    expected_f = 0
    assert_array_almost_equal(f, [expected_f, 1 / 1.5, 1, expected_f], 2)
    assert_array_almost_equal(s, [1, 2, 1, 0], 2)

    f2 = fbeta_score(y_true, y_pred, beta=2, average=None, zero_division=zero_division)
    support = s
    assert_array_almost_equal(f2, [expected_f, 0.55, 1, expected_f], 2)

    p, r, f, s = precision_recall_fscore_support(
        y_true, y_pred, average="macro", zero_division=zero_division
    )

    value_to_sum = 0 if np.isnan(zero_division_expected) else zero_division_expected
    values_to_average = 3 + (not np.isnan(zero_division_expected))

    assert_almost_equal(p, (2 + value_to_sum) / values_to_average)
    assert_almost_equal(r, (1.5 + value_to_sum) / values_to_average)
    expected_f = (2 / 3 + 1) / 4
    assert_almost_equal(f, expected_f)
    assert s is None
    assert_almost_equal(
        fbeta_score(
            y_true,
            y_pred,
            beta=2,
            average="macro",
            zero_division=zero_division,
        ),
        _nanaverage(f2, weights=None),
    )

    p, r, f, s = precision_recall_fscore_support(
        y_true, y_pred, average="micro", zero_division=zero_division
    )
    assert_almost_equal(p, 2 / 3)
    assert_almost_equal(r, 0.5)
    assert_almost_equal(f, 2 / 3 / (2 / 3 + 0.5))
    assert s is None
    assert_almost_equal(
        fbeta_score(
            y_true, y_pred, beta=2, average="micro", zero_division=zero_division
        ),
        (1 + 4) * p * r / (4 * p + r),
    )

    p, r, f, s = precision_recall_fscore_support(
        y_true, y_pred, average="weighted", zero_division=zero_division
    )
    assert_almost_equal(p, 3 / 4 if zero_division_expected == 0 else 1.0)
    assert_almost_equal(r, 0.5)
    values_to_average = 4
    assert_almost_equal(f, (2 * 2 / 3 + 1) / values_to_average)
    assert s is None
    assert_almost_equal(
        fbeta_score(
            y_true, y_pred, beta=2, average="weighted", zero_division=zero_division
        ),
        _nanaverage(f2, weights=support),
    )

    p, r, f, s = precision_recall_fscore_support(y_true, y_pred, average="samples")
    # |h(x_i) inter y_i | = [0, 0, 2]
    # |y_i| = [1, 1, 2]
    # |h(x_i)| = [0, 1, 2]
    assert_almost_equal(p, 1 / 3)
    assert_almost_equal(r, 1 / 3)
    assert_almost_equal(f, 1 / 3)
    assert s is None
    expected_result = 0.333
    assert_almost_equal(
        fbeta_score(
            y_true, y_pred, beta=2, average="samples", zero_division=zero_division
        ),
        expected_result,
        2,
    )


@pytest.mark.parametrize("beta", [1])
@pytest.mark.parametrize("average", ["macro", "micro", "weighted", "samples"])
@pytest.mark.parametrize("zero_division", [0, 1, np.nan])
def test_precision_recall_f1_no_labels(beta, average, zero_division):
    y_true = np.zeros((20, 3))
    y_pred = np.zeros_like(y_true)

    with warnings.catch_warnings():
        warnings.simplefilter("error")

        p, r, f, s = precision_recall_fscore_support(
            y_true,
            y_pred,
            average=average,
            beta=beta,
            zero_division=zero_division,
        )
        fbeta = fbeta_score(
            y_true,
            y_pred,
            beta=beta,
            average=average,
            zero_division=zero_division,
        )
    assert s is None

    # if zero_division = nan, check that all metrics are nan and exit
    if np.isnan(zero_division):
        for metric in [p, r, f, fbeta]:
            assert np.isnan(metric)
        return

    zero_division = float(zero_division)
    assert_almost_equal(p, zero_division)
    assert_almost_equal(r, zero_division)
    assert_almost_equal(f, zero_division)

    assert_almost_equal(fbeta, float(zero_division))


@pytest.mark.parametrize("average", ["macro", "micro", "weighted", "samples"])
def test_precision_recall_f1_no_labels_check_warnings(average):
    y_true = np.zeros((20, 3))
    y_pred = np.zeros_like(y_true)

    func = precision_recall_fscore_support
    with pytest.warns(UndefinedMetricWarning):
        p, r, f, s = func(y_true, y_pred, average=average, beta=1.0)

    assert_almost_equal(p, 0)
    assert_almost_equal(r, 0)
    assert_almost_equal(f, 0)
    assert s is None

    with pytest.warns(UndefinedMetricWarning):
        fbeta = fbeta_score(y_true, y_pred, average=average, beta=1.0)

    assert_almost_equal(fbeta, 0)


@pytest.mark.parametrize("zero_division", [0, 1, np.nan])
def test_precision_recall_f1_no_labels_average_none(zero_division):
    y_true = np.zeros((20, 3))
    y_pred = np.zeros_like(y_true)

    # tp = [0, 0, 0]
    # fn = [0, 0, 0]
    # fp = [0, 0, 0]
    # support = [0, 0, 0]
    # |y_hat_i inter y_i | = [0, 0, 0]
    # |y_i| = [0, 0, 0]
    # |y_hat_i| = [0, 0, 0]

    with warnings.catch_warnings():
        warnings.simplefilter("error")

        p, r, f, s = precision_recall_fscore_support(
            y_true,
            y_pred,
            average=None,
            beta=1.0,
            zero_division=zero_division,
        )
        fbeta = fbeta_score(
            y_true, y_pred, beta=1.0, average=None, zero_division=zero_division
        )

    zero_division = np.float64(zero_division)
    assert_array_almost_equal(p, [zero_division, zero_division, zero_division], 2)
    assert_array_almost_equal(r, [zero_division, zero_division, zero_division], 2)
    assert_array_almost_equal(f, [zero_division, zero_division, zero_division], 2)
    assert_array_almost_equal(s, [0, 0, 0], 2)

    assert_array_almost_equal(fbeta, [zero_division, zero_division, zero_division], 2)


def test_precision_recall_f1_no_labels_average_none_warn():
    y_true = np.zeros((20, 3))
    y_pred = np.zeros_like(y_true)

    # tp = [0, 0, 0]
    # fn = [0, 0, 0]
    # fp = [0, 0, 0]
    # support = [0, 0, 0]
    # |y_hat_i inter y_i | = [0, 0, 0]
    # |y_i| = [0, 0, 0]
    # |y_hat_i| = [0, 0, 0]

    with pytest.warns(UndefinedMetricWarning):
        p, r, f, s = precision_recall_fscore_support(
            y_true, y_pred, average=None, beta=1
        )

    assert_array_almost_equal(p, [0, 0, 0], 2)
    assert_array_almost_equal(r, [0, 0, 0], 2)
    assert_array_almost_equal(f, [0, 0, 0], 2)
    assert_array_almost_equal(s, [0, 0, 0], 2)

    with pytest.warns(UndefinedMetricWarning):
        fbeta = fbeta_score(y_true, y_pred, beta=1, average=None)

    assert_array_almost_equal(fbeta, [0, 0, 0], 2)


def test_prf_warnings():
    # average of per-label scores
    f, w = precision_recall_fscore_support, UndefinedMetricWarning
    for average in [None, "weighted", "macro"]:
        msg = (
            "Precision is ill-defined and "
            "being set to 0.0 in labels with no predicted samples."
            " Use `zero_division` parameter to control"
            " this behavior."
        )
        with pytest.warns(w, match=msg):
            f([0, 1, 2], [1, 1, 2], average=average)

        msg = (
            "Recall is ill-defined and "
            "being set to 0.0 in labels with no true samples."
            " Use `zero_division` parameter to control"
            " this behavior."
        )
        with pytest.warns(w, match=msg):
            f([1, 1, 2], [0, 1, 2], average=average)

    # average of per-sample scores
    msg = (
        "Precision is ill-defined and "
        "being set to 0.0 in samples with no predicted labels."
        " Use `zero_division` parameter to control"
        " this behavior."
    )
    with pytest.warns(w, match=msg):
        f(np.array([[1, 0], [1, 0]]), np.array([[1, 0], [0, 0]]), average="samples")

    msg = (
        "Recall is ill-defined and "
        "being set to 0.0 in samples with no true labels."
        " Use `zero_division` parameter to control"
        " this behavior."
    )
    with pytest.warns(w, match=msg):
        f(np.array([[1, 0], [0, 0]]), np.array([[1, 0], [1, 0]]), average="samples")

    # single score: micro-average
    msg = (
        "Precision is ill-defined and "
        "being set to 0.0 due to no predicted samples."
        " Use `zero_division` parameter to control"
        " this behavior."
    )
    with pytest.warns(w, match=msg):
        f(np.array([[1, 1], [1, 1]]), np.array([[0, 0], [0, 0]]), average="micro")

    msg = (
        "Recall is ill-defined and "
        "being set to 0.0 due to no true samples."
        " Use `zero_division` parameter to control"
        " this behavior."
    )
    with pytest.warns(w, match=msg):
        f(np.array([[0, 0], [0, 0]]), np.array([[1, 1], [1, 1]]), average="micro")

    # single positive label
    msg = (
        "Precision is ill-defined and "
        "being set to 0.0 due to no predicted samples."
        " Use `zero_division` parameter to control"
        " this behavior."
    )
    with pytest.warns(w, match=msg):
        f([1, 1], [-1, -1], average="binary")

    msg = (
        "Recall is ill-defined and "
        "being set to 0.0 due to no true samples."
        " Use `zero_division` parameter to control"
        " this behavior."
    )
    with pytest.warns(w, match=msg):
        f([-1, -1], [1, 1], average="binary")

    with warnings.catch_warnings(record=True) as record:
        warnings.simplefilter("always")
        precision_recall_fscore_support([0, 0], [0, 0], average="binary")
        msg = (
            "F-score is ill-defined and being set to 0.0 due to no true nor "
            "predicted samples. Use `zero_division` parameter to control this"
            " behavior."
        )
        assert str(record.pop().message) == msg
        msg = (
            "Recall is ill-defined and "
            "being set to 0.0 due to no true samples."
            " Use `zero_division` parameter to control"
            " this behavior."
        )
        assert str(record.pop().message) == msg
        msg = (
            "Precision is ill-defined and "
            "being set to 0.0 due to no predicted samples."
            " Use `zero_division` parameter to control"
            " this behavior."
        )
        assert str(record.pop().message) == msg


@pytest.mark.parametrize("zero_division", [0, 1, np.nan])
def test_prf_no_warnings_if_zero_division_set(zero_division):
    with warnings.catch_warnings():
        warnings.simplefilter("error")

        # average of per-label scores
        for average in [None, "weighted", "macro"]:
            precision_recall_fscore_support(
                [0, 1, 2], [1, 1, 2], average=average, zero_division=zero_division
            )

            precision_recall_fscore_support(
                [1, 1, 2], [0, 1, 2], average=average, zero_division=zero_division
            )

        # average of per-sample scores
        precision_recall_fscore_support(
            np.array([[1, 0], [1, 0]]),
            np.array([[1, 0], [0, 0]]),
            average="samples",
            zero_division=zero_division,
        )

        precision_recall_fscore_support(
            np.array([[1, 0], [0, 0]]),
            np.array([[1, 0], [1, 0]]),
            average="samples",
            zero_division=zero_division,
        )

        # single score: micro-average
        precision_recall_fscore_support(
            np.array([[1, 1], [1, 1]]),
            np.array([[0, 0], [0, 0]]),
            average="micro",
            zero_division=zero_division,
        )

        precision_recall_fscore_support(
            np.array([[0, 0], [0, 0]]),
            np.array([[1, 1], [1, 1]]),
            average="micro",
            zero_division=zero_division,
        )

        # single positive label
        precision_recall_fscore_support(
            [1, 1], [-1, -1], average="binary", zero_division=zero_division
        )

        precision_recall_fscore_support(
            [-1, -1], [1, 1], average="binary", zero_division=zero_division
        )

    with warnings.catch_warnings(record=True) as record:
        warnings.simplefilter("always")
        precision_recall_fscore_support(
            [0, 0], [0, 0], average="binary", zero_division=zero_division
        )
        assert len(record) == 0


@pytest.mark.parametrize("zero_division", ["warn", 0, 1, np.nan])
def test_recall_warnings(zero_division):
    with warnings.catch_warnings():
        warnings.simplefilter("error")

        recall_score(
            np.array([[1, 1], [1, 1]]),
            np.array([[0, 0], [0, 0]]),
            average="micro",
            zero_division=zero_division,
        )

    with warnings.catch_warnings(record=True) as record:
        warnings.simplefilter("always")
        recall_score(
            np.array([[0, 0], [0, 0]]),
            np.array([[1, 1], [1, 1]]),
            average="micro",
            zero_division=zero_division,
        )
        if zero_division == "warn":
            assert (
                str(record.pop().message) == "Recall is ill-defined and "
                "being set to 0.0 due to no true samples."
                " Use `zero_division` parameter to control"
                " this behavior."
            )
        else:
            assert len(record) == 0

        recall_score([0, 0], [0, 0])
        if zero_division == "warn":
            assert (
                str(record.pop().message) == "Recall is ill-defined and "
                "being set to 0.0 due to no true samples."
                " Use `zero_division` parameter to control"
                " this behavior."
            )


@pytest.mark.parametrize("zero_division", ["warn", 0, 1, np.nan])
def test_precision_warnings(zero_division):
    with warnings.catch_warnings(record=True) as record:
        warnings.simplefilter("always")
        precision_score(
            np.array([[1, 1], [1, 1]]),
            np.array([[0, 0], [0, 0]]),
            average="micro",
            zero_division=zero_division,
        )
        if zero_division == "warn":
            assert (
                str(record.pop().message) == "Precision is ill-defined and "
                "being set to 0.0 due to no predicted samples."
                " Use `zero_division` parameter to control"
                " this behavior."
            )
        else:
            assert len(record) == 0

        precision_score([0, 0], [0, 0])
        if zero_division == "warn":
            assert (
                str(record.pop().message) == "Precision is ill-defined and "
                "being set to 0.0 due to no predicted samples."
                " Use `zero_division` parameter to control"
                " this behavior."
            )

    with warnings.catch_warnings():
        warnings.simplefilter("error")

        precision_score(
            np.array([[0, 0], [0, 0]]),
            np.array([[1, 1], [1, 1]]),
            average="micro",
            zero_division=zero_division,
        )


@pytest.mark.parametrize("zero_division", ["warn", 0, 1, np.nan])
def test_fscore_warnings(zero_division):
    with warnings.catch_warnings(record=True) as record:
        warnings.simplefilter("always")

        for score in [f1_score, partial(fbeta_score, beta=2)]:
            score(
                np.array([[1, 1], [1, 1]]),
                np.array([[0, 0], [0, 0]]),
                average="micro",
                zero_division=zero_division,
            )
            assert len(record) == 0

            score(
                np.array([[0, 0], [0, 0]]),
                np.array([[1, 1], [1, 1]]),
                average="micro",
                zero_division=zero_division,
            )
            assert len(record) == 0

            score(
                np.array([[0, 0], [0, 0]]),
                np.array([[0, 0], [0, 0]]),
                average="micro",
                zero_division=zero_division,
            )
            if zero_division == "warn":
                assert (
                    str(record.pop().message) == "F-score is ill-defined and "
                    "being set to 0.0 due to no true nor predicted "
                    "samples. Use `zero_division` parameter to "
                    "control this behavior."
                )
            else:
                assert len(record) == 0


def test_prf_average_binary_data_non_binary():
    # Error if user does not explicitly set non-binary average mode
    y_true_mc = [1, 2, 3, 3]
    y_pred_mc = [1, 2, 3, 1]
    msg_mc = (
        r"Target is multiclass but average='binary'. Please "
        r"choose another average setting, one of \["
        r"None, 'micro', 'macro', 'weighted'\]."
    )
    y_true_ind = np.array([[0, 1, 1], [1, 0, 0], [0, 0, 1]])
    y_pred_ind = np.array([[0, 1, 0], [1, 0, 0], [0, 0, 1]])
    msg_ind = (
        r"Target is multilabel-indicator but average='binary'. Please "
        r"choose another average setting, one of \["
        r"None, 'micro', 'macro', 'weighted', 'samples'\]."
    )

    for y_true, y_pred, msg in [
        (y_true_mc, y_pred_mc, msg_mc),
        (y_true_ind, y_pred_ind, msg_ind),
    ]:
        for metric in [
            precision_score,
            recall_score,
            f1_score,
            partial(fbeta_score, beta=2),
        ]:
            with pytest.raises(ValueError, match=msg):
                metric(y_true, y_pred)


def test__check_targets():
    # Check that _check_targets correctly merges target types, squeezes
    # output and fails if input lengths differ.
    IND = "multilabel-indicator"
    MC = "multiclass"
    BIN = "binary"
    CNT = "continuous"
    MMC = "multiclass-multioutput"
    MCN = "continuous-multioutput"
    # all of length 3
    EXAMPLES = [
        (IND, np.array([[0, 1, 1], [1, 0, 0], [0, 0, 1]])),
        # must not be considered binary
        (IND, np.array([[0, 1], [1, 0], [1, 1]])),
        (MC, [2, 3, 1]),
        (BIN, [0, 1, 1]),
        (CNT, [0.0, 1.5, 1.0]),
        (MC, np.array([[2], [3], [1]])),
        (BIN, np.array([[0], [1], [1]])),
        (CNT, np.array([[0.0], [1.5], [1.0]])),
        (MMC, np.array([[0, 2], [1, 3], [2, 3]])),
        (MCN, np.array([[0.5, 2.0], [1.1, 3.0], [2.0, 3.0]])),
    ]
    # expected type given input types, or None for error
    # (types will be tried in either order)
    EXPECTED = {
        (IND, IND): IND,
        (MC, MC): MC,
        (BIN, BIN): BIN,
        (MC, IND): None,
        (BIN, IND): None,
        (BIN, MC): MC,
        # Disallowed types
        (CNT, CNT): None,
        (MMC, MMC): None,
        (MCN, MCN): None,
        (IND, CNT): None,
        (MC, CNT): None,
        (BIN, CNT): None,
        (MMC, CNT): None,
        (MCN, CNT): None,
        (IND, MMC): None,
        (MC, MMC): None,
        (BIN, MMC): None,
        (MCN, MMC): None,
        (IND, MCN): None,
        (MC, MCN): None,
        (BIN, MCN): None,
    }

    for (type1, y1), (type2, y2) in product(EXAMPLES, repeat=2):
        try:
            expected = EXPECTED[type1, type2]
        except KeyError:
            expected = EXPECTED[type2, type1]
        if expected is None:
            with pytest.raises(ValueError):
                _check_targets(y1, y2)

            if type1 != type2:
                err_msg = (
                    "Classification metrics can't handle a mix "
                    "of {0} and {1} targets".format(type1, type2)
                )
                with pytest.raises(ValueError, match=err_msg):
                    _check_targets(y1, y2)

            else:
                if type1 not in (BIN, MC, IND):
                    err_msg = "{0} is not supported".format(type1)
                    with pytest.raises(ValueError, match=err_msg):
                        _check_targets(y1, y2)

        else:
            merged_type, y1out, y2out = _check_targets(y1, y2)
            assert merged_type == expected
            if merged_type.startswith("multilabel"):
                assert y1out.format == "csr"
                assert y2out.format == "csr"
            else:
                assert_array_equal(y1out, np.squeeze(y1))
                assert_array_equal(y2out, np.squeeze(y2))
            with pytest.raises(ValueError):
                _check_targets(y1[:-1], y2)

    # Make sure seq of seq is not supported
    y1 = [(1, 2), (0, 2, 3)]
    y2 = [(2,), (0, 2)]
    msg = (
        "You appear to be using a legacy multi-label data representation. "
        "Sequence of sequences are no longer supported; use a binary array"
        " or sparse matrix instead - the MultiLabelBinarizer"
        " transformer can convert to this format."
    )
    with pytest.raises(ValueError, match=msg):
        _check_targets(y1, y2)


def test__check_targets_multiclass_with_both_y_true_and_y_pred_binary():
    # https://github.com/scikit-learn/scikit-learn/issues/8098
    y_true = [0, 1]
    y_pred = [0, -1]
    assert _check_targets(y_true, y_pred)[0] == "multiclass"


def test_hinge_loss_binary():
    y_true = np.array([-1, 1, 1, -1])
    pred_decision = np.array([-8.5, 0.5, 1.5, -0.3])
    assert hinge_loss(y_true, pred_decision) == 1.2 / 4

    y_true = np.array([0, 2, 2, 0])
    pred_decision = np.array([-8.5, 0.5, 1.5, -0.3])
    assert hinge_loss(y_true, pred_decision) == 1.2 / 4


def test_hinge_loss_multiclass():
    pred_decision = np.array(
        [
            [+0.36, -0.17, -0.58, -0.99],
            [-0.54, -0.37, -0.48, -0.58],
            [-1.45, -0.58, -0.38, -0.17],
            [-0.54, -0.38, -0.48, -0.58],
            [-2.36, -0.79, -0.27, +0.24],
            [-1.45, -0.58, -0.38, -0.17],
        ]
    )
    y_true = np.array([0, 1, 2, 1, 3, 2])
    dummy_losses = np.array(
        [
            1 - pred_decision[0][0] + pred_decision[0][1],
            1 - pred_decision[1][1] + pred_decision[1][2],
            1 - pred_decision[2][2] + pred_decision[2][3],
            1 - pred_decision[3][1] + pred_decision[3][2],
            1 - pred_decision[4][3] + pred_decision[4][2],
            1 - pred_decision[5][2] + pred_decision[5][3],
        ]
    )
    np.clip(dummy_losses, 0, None, out=dummy_losses)
    dummy_hinge_loss = np.mean(dummy_losses)
    assert hinge_loss(y_true, pred_decision) == dummy_hinge_loss


def test_hinge_loss_multiclass_missing_labels_with_labels_none():
    y_true = np.array([0, 1, 2, 2])
    pred_decision = np.array(
        [
            [+1.27, 0.034, -0.68, -1.40],
            [-1.45, -0.58, -0.38, -0.17],
            [-2.36, -0.79, -0.27, +0.24],
            [-2.36, -0.79, -0.27, +0.24],
        ]
    )
    error_message = (
        "Please include all labels in y_true or pass labels as third argument"
    )
    with pytest.raises(ValueError, match=error_message):
        hinge_loss(y_true, pred_decision)


def test_hinge_loss_multiclass_no_consistent_pred_decision_shape():
    # test for inconsistency between multiclass problem and pred_decision
    # argument
    y_true = np.array([2, 1, 0, 1, 0, 1, 1])
    pred_decision = np.array([0, 1, 2, 1, 0, 2, 1])
    error_message = (
        "The shape of pred_decision cannot be 1d array"
        "with a multiclass target. pred_decision shape "
        "must be (n_samples, n_classes), that is "
        "(7, 3). Got: (7,)"
    )
    with pytest.raises(ValueError, match=re.escape(error_message)):
        hinge_loss(y_true=y_true, pred_decision=pred_decision)

    # test for inconsistency between pred_decision shape and labels number
    pred_decision = np.array([[0, 1], [0, 1], [0, 1], [0, 1], [2, 0], [0, 1], [1, 0]])
    labels = [0, 1, 2]
    error_message = (
        "The shape of pred_decision is not "
        "consistent with the number of classes. "
        "With a multiclass target, pred_decision "
        "shape must be (n_samples, n_classes), that is "
        "(7, 3). Got: (7, 2)"
    )
    with pytest.raises(ValueError, match=re.escape(error_message)):
        hinge_loss(y_true=y_true, pred_decision=pred_decision, labels=labels)


def test_hinge_loss_multiclass_with_missing_labels():
    pred_decision = np.array(
        [
            [+0.36, -0.17, -0.58, -0.99],
            [-0.55, -0.38, -0.48, -0.58],
            [-1.45, -0.58, -0.38, -0.17],
            [-0.55, -0.38, -0.48, -0.58],
            [-1.45, -0.58, -0.38, -0.17],
        ]
    )
    y_true = np.array([0, 1, 2, 1, 2])
    labels = np.array([0, 1, 2, 3])
    dummy_losses = np.array(
        [
            1 - pred_decision[0][0] + pred_decision[0][1],
            1 - pred_decision[1][1] + pred_decision[1][2],
            1 - pred_decision[2][2] + pred_decision[2][3],
            1 - pred_decision[3][1] + pred_decision[3][2],
            1 - pred_decision[4][2] + pred_decision[4][3],
        ]
    )
    np.clip(dummy_losses, 0, None, out=dummy_losses)
    dummy_hinge_loss = np.mean(dummy_losses)
    assert hinge_loss(y_true, pred_decision, labels=labels) == dummy_hinge_loss


def test_hinge_loss_multiclass_missing_labels_only_two_unq_in_y_true():
    # non-regression test for:
    # https://github.com/scikit-learn/scikit-learn/issues/17630
    # check that we can compute the hinge loss when providing an array
    # with labels allowing to not have all labels in y_true
    pred_decision = np.array(
        [
            [+0.36, -0.17, -0.58],
            [-0.15, -0.58, -0.48],
            [-1.45, -0.58, -0.38],
            [-0.55, -0.78, -0.42],
            [-1.45, -0.58, -0.38],
        ]
    )
    y_true = np.array([0, 2, 2, 0, 2])
    labels = np.array([0, 1, 2])
    dummy_losses = np.array(
        [
            1 - pred_decision[0][0] + pred_decision[0][1],
            1 - pred_decision[1][2] + pred_decision[1][0],
            1 - pred_decision[2][2] + pred_decision[2][1],
            1 - pred_decision[3][0] + pred_decision[3][2],
            1 - pred_decision[4][2] + pred_decision[4][1],
        ]
    )
    np.clip(dummy_losses, 0, None, out=dummy_losses)
    dummy_hinge_loss = np.mean(dummy_losses)
    assert_almost_equal(
        hinge_loss(y_true, pred_decision, labels=labels), dummy_hinge_loss
    )


def test_hinge_loss_multiclass_invariance_lists():
    # Currently, invariance of string and integer labels cannot be tested
    # in common invariance tests because invariance tests for multiclass
    # decision functions is not implemented yet.
    y_true = ["blue", "green", "red", "green", "white", "red"]
    pred_decision = [
        [+0.36, -0.17, -0.58, -0.99],
        [-0.55, -0.38, -0.48, -0.58],
        [-1.45, -0.58, -0.38, -0.17],
        [-0.55, -0.38, -0.48, -0.58],
        [-2.36, -0.79, -0.27, +0.24],
        [-1.45, -0.58, -0.38, -0.17],
    ]
    dummy_losses = np.array(
        [
            1 - pred_decision[0][0] + pred_decision[0][1],
            1 - pred_decision[1][1] + pred_decision[1][2],
            1 - pred_decision[2][2] + pred_decision[2][3],
            1 - pred_decision[3][1] + pred_decision[3][2],
            1 - pred_decision[4][3] + pred_decision[4][2],
            1 - pred_decision[5][2] + pred_decision[5][3],
        ]
    )
    np.clip(dummy_losses, 0, None, out=dummy_losses)
    dummy_hinge_loss = np.mean(dummy_losses)
    assert hinge_loss(y_true, pred_decision) == dummy_hinge_loss


def test_log_loss():
    # binary case with symbolic labels ("no" < "yes")
    y_true = ["no", "no", "no", "yes", "yes", "yes"]
    y_pred = np.array(
        [[0.5, 0.5], [0.1, 0.9], [0.01, 0.99], [0.9, 0.1], [0.75, 0.25], [0.001, 0.999]]
    )
    loss = log_loss(y_true, y_pred)
    loss_true = -np.mean(bernoulli.logpmf(np.array(y_true) == "yes", y_pred[:, 1]))
    assert_allclose(loss, loss_true)

    # multiclass case; adapted from http://bit.ly/RJJHWA
    y_true = [1, 0, 2]
    y_pred = [[0.2, 0.7, 0.1], [0.6, 0.2, 0.2], [0.6, 0.1, 0.3]]
    loss = log_loss(y_true, y_pred, normalize=True)
    assert_allclose(loss, 0.6904911)

    # check that we got all the shapes and axes right
    # by doubling the length of y_true and y_pred
    y_true *= 2
    y_pred *= 2
    loss = log_loss(y_true, y_pred, normalize=False)
    assert_allclose(loss, 0.6904911 * 6)

    # raise error if number of classes are not equal.
    y_true = [1, 0, 2]
    y_pred = [[0.3, 0.7], [0.6, 0.4], [0.4, 0.6]]
    with pytest.raises(ValueError):
        log_loss(y_true, y_pred)

    # raise error if labels do not contain all values of y_true
    y_true = ["a", "b", "c"]
    y_pred = [[0.9, 0.1, 0.0], [0.1, 0.9, 0.0], [0.1, 0.1, 0.8]]
    labels = ["a", "c", "d"]
    error_str = (
        "y_true contains values {'b'} not belonging to the passed "
        "labels ['a', 'c', 'd']."
    )
    with pytest.raises(ValueError, match=re.escape(error_str)):
        log_loss(y_true, y_pred, labels=labels)

    # case when y_true is a string array object
    y_true = ["ham", "spam", "spam", "ham"]
    y_pred = [[0.3, 0.7], [0.6, 0.4], [0.4, 0.6], [0.7, 0.3]]
    loss = log_loss(y_true, y_pred)
    assert_allclose(loss, 0.7469410)

    # test labels option

    y_true = [2, 2]
    y_pred = [[0.2, 0.8], [0.6, 0.4]]
    y_score = np.array([[0.1, 0.9], [0.1, 0.9]])
    error_str = (
        "y_true contains only one label (2). Please provide the list of all "
        "expected class labels explicitly through the labels argument."
    )
    with pytest.raises(ValueError, match=re.escape(error_str)):
        log_loss(y_true, y_pred)

    y_pred = [[0.2, 0.8], [0.6, 0.4], [0.7, 0.3]]
    error_str = "Found input variables with inconsistent numbers of samples: [3, 2]"
    with pytest.raises(ValueError, match=re.escape(error_str)):
        log_loss(y_true, y_pred)

    # works when the labels argument is used

    true_log_loss = -np.mean(np.log(y_score[:, 1]))
    calculated_log_loss = log_loss(y_true, y_score, labels=[1, 2])
    assert_allclose(calculated_log_loss, true_log_loss)

    # ensure labels work when len(np.unique(y_true)) != y_pred.shape[1]
    y_true = [1, 2, 2]
    y_score2 = [[0.7, 0.1, 0.2], [0.2, 0.7, 0.1], [0.1, 0.7, 0.2]]
    loss = log_loss(y_true, y_score2, labels=[1, 2, 3])
    assert_allclose(loss, -np.log(0.7))


@pytest.mark.parametrize("dtype", [np.float64, np.float32, np.float16])
def test_log_loss_eps(dtype):
    """Check the behaviour internal eps that changes depending on the input dtype.

    Non-regression test for:
    https://github.com/scikit-learn/scikit-learn/issues/24315
    """
    y_true = np.array([0, 1], dtype=dtype)
    y_pred = np.array([1, 0], dtype=dtype)

    loss = log_loss(y_true, y_pred)
    assert np.isfinite(loss)


@pytest.mark.parametrize("dtype", [np.float64, np.float32, np.float16])
def test_log_loss_not_probabilities_warning(dtype):
    """Check that log_loss raises a warning when y_pred values don't sum to 1."""
    y_true = np.array([0, 1, 1, 0])
    y_pred = np.array([[0.2, 0.7], [0.6, 0.3], [0.4, 0.7], [0.8, 0.3]], dtype=dtype)

    with pytest.warns(UserWarning, match="The y_prob values do not sum to one."):
        log_loss(y_true, y_pred)


@pytest.mark.parametrize(
    "y_true, y_pred",
    [
        ([0, 1, 0], [0, 1, 0]),
        ([0, 1, 0], [[1, 0], [0, 1], [1, 0]]),
        ([0, 1, 2], [[1, 0, 0], [0, 1, 0], [0, 0, 1]]),
    ],
)
def test_log_loss_perfect_predictions(y_true, y_pred):
    """Check that log_loss returns 0 for perfect predictions."""
    # Because of the clipping, the result is not exactly 0
    assert log_loss(y_true, y_pred) == pytest.approx(0)


def test_log_loss_pandas_input():
    # case when input is a pandas series and dataframe gh-5715
    y_tr = np.array(["ham", "spam", "spam", "ham"])
    y_pr = np.array([[0.3, 0.7], [0.6, 0.4], [0.4, 0.6], [0.7, 0.3]])
    types = [(MockDataFrame, MockDataFrame)]
    try:
        from pandas import DataFrame, Series

        types.append((Series, DataFrame))
    except ImportError:
        pass
    for TrueInputType, PredInputType in types:
        # y_pred dataframe, y_true series
        y_true, y_pred = TrueInputType(y_tr), PredInputType(y_pr)
        loss = log_loss(y_true, y_pred)
        assert_allclose(loss, 0.7469410)


def test_log_loss_warnings():
    expected_message = re.escape(
        "Labels passed were ['spam', 'eggs', 'ham']. But this function "
        "assumes labels are ordered lexicographically. "
        "Pass the ordered labels=['eggs', 'ham', 'spam'] and ensure that "
        "the columns of y_prob correspond to this ordering."
    )
    with pytest.warns(UserWarning, match=expected_message):
        log_loss(
            ["eggs", "spam", "ham"],
            [[1, 0, 0], [0, 1, 0], [0, 0, 1]],
            labels=["spam", "eggs", "ham"],
        )


def test_brier_score_loss_binary():
    # Check brier_score_loss function
    y_true = np.array([0, 1, 1, 0, 1, 1])
    y_prob = np.array([0.1, 0.8, 0.9, 0.3, 1.0, 0.95])
    true_score = linalg.norm(y_true - y_prob) ** 2 / len(y_true)

    assert_almost_equal(brier_score_loss(y_true, y_true), 0.0)
    assert_almost_equal(brier_score_loss(y_true, y_prob), true_score)
    assert_almost_equal(brier_score_loss(1.0 + y_true, y_prob), true_score)
    assert_almost_equal(brier_score_loss(2 * y_true - 1, y_prob), true_score)

    # check that using (n_samples, 2) y_prob or y_true gives the same score
    y_prob_reshaped = np.column_stack((1 - y_prob, y_prob))
    y_true_reshaped = np.column_stack((1 - y_true, y_true))
    assert_almost_equal(brier_score_loss(y_true, y_prob_reshaped), true_score)
    assert_almost_equal(brier_score_loss(y_true_reshaped, y_prob_reshaped), true_score)

    # check scale_by_half argument
    assert_almost_equal(
        brier_score_loss(y_true, y_prob, scale_by_half="auto"), true_score
    )
    assert_almost_equal(
        brier_score_loss(y_true, y_prob, scale_by_half=True), true_score
    )
    assert_almost_equal(
        brier_score_loss(y_true, y_prob, scale_by_half=False), 2 * true_score
    )

    # calculate correctly when there's only one class in y_true
    assert_almost_equal(brier_score_loss([-1], [0.4]), 0.4**2)
    assert_almost_equal(brier_score_loss([0], [0.4]), 0.4**2)
    assert_almost_equal(brier_score_loss([1], [0.4]), (1 - 0.4) ** 2)
    assert_almost_equal(brier_score_loss(["foo"], [0.4], pos_label="bar"), 0.4**2)
    assert_almost_equal(
        brier_score_loss(["foo"], [0.4], pos_label="foo"),
        (1 - 0.4) ** 2,
    )


def test_brier_score_loss_multiclass():
    # test cases for multi-class
    assert_almost_equal(
        brier_score_loss(
            ["eggs", "spam", "ham"],
            [[1, 0, 0, 0], [0, 1, 0, 0], [0, 1, 0, 0]],
            labels=["eggs", "ham", "spam", "yams"],
        ),
        2 / 3,
    )

    assert_almost_equal(
        brier_score_loss(
            [1, 0, 2], [[0.2, 0.7, 0.1], [0.6, 0.2, 0.2], [0.6, 0.1, 0.3]]
        ),
        0.41333333,
    )

    # check perfect predictions for 3 classes
    assert_almost_equal(
        brier_score_loss(
            [0, 1, 2], [[1.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 1.0]]
        ),
        0,
    )

    # check perfectly incorrect predictions for 3 classes
    assert_almost_equal(
        brier_score_loss(
            [0, 1, 2], [[0.0, 1.0, 0.0], [1.0, 0.0, 0.0], [1.0, 0.0, 0.0]]
        ),
        2,
    )


def test_brier_score_loss_invalid_inputs():
    # binary case
    y_true = np.array([0, 1, 1, 0, 1, 1])
    y_prob = np.array([0.1, 0.8, 0.9, 0.3, 1.0, 0.95])
    with pytest.raises(ValueError):
        # bad length of y_prob
        brier_score_loss(y_true, y_prob[1:])
    with pytest.raises(ValueError):
        # y_pred has value greater than 1
        brier_score_loss(y_true, y_prob + 1.0)
    with pytest.raises(ValueError):
        # y_pred has value less than 0
        brier_score_loss(y_true, y_prob - 1.0)

    # multiclass case
    y_true = np.array([1, 0, 2])
    y_prob = np.array([[0.2, 0.7, 0.1], [0.6, 0.2, 0.2], [0.6, 0.1, 0.3]])
    with pytest.raises(ValueError):
        # bad length of y_pred
        brier_score_loss(y_true, y_prob[1:])
    with pytest.raises(ValueError):
        # y_pred has value greater than 1
        brier_score_loss(y_true, y_prob + 1.0)
    with pytest.raises(ValueError):
        # y_pred has value less than 0
        brier_score_loss(y_true, y_prob - 1.0)

    # raise an error for multiclass y_true and binary y_prob
    y_true = np.array([0, 1, 2, 0])
    y_prob = np.array([0.8, 0.6, 0.4, 0.2])
    error_message = re.escape(
        "The type of the target inferred from y_true is multiclass "
        "but should be binary according to the shape of y_prob."
    )
    with pytest.raises(ValueError, match=error_message):
        brier_score_loss(y_true, y_prob)

    # raise an error for wrong number of classes
    y_true = [0, 1, 2]
    y_prob = [[1, 0], [0, 1], [0, 1]]
    error_message = (
        "y_true and y_prob contain different number of "
        "classes: 3 vs 2. Please provide the true "
        "labels explicitly through the labels argument. "
        "Classes found in "
        "y_true: [0 1 2]"
    )
    with pytest.raises(ValueError, match=re.escape(error_message)):
        brier_score_loss(y_true, y_prob)

    y_true = ["eggs", "spam", "ham"]
    y_prob = [[1, 0, 0], [0, 1, 0], [0, 1, 0]]
    labels = ["eggs", "spam", "ham", "yams"]
    error_message = (
        "The number of classes in labels is different "
        "from that in y_prob. Classes found in "
        "labels: ['eggs' 'ham' 'spam' 'yams']"
    )
    with pytest.raises(ValueError, match=re.escape(error_message)):
        brier_score_loss(y_true, y_prob, labels=labels)

    # raise error message when there's only one class in y_true
    y_true = ["eggs"]
    y_prob = [[0.9, 0.1]]
    error_message = (
        "y_true contains only one label (eggs). Please "
        "provide the list of all expected class labels explicitly through the "
        "labels argument."
    )
    with pytest.raises(ValueError, match=re.escape(error_message)):
        brier_score_loss(y_true, y_prob)

    # error is fixed when labels is specified
    assert_almost_equal(brier_score_loss(y_true, y_prob, labels=["eggs", "ham"]), 0.01)


def test_brier_score_loss_warnings():
    expected_message = re.escape(
        "Labels passed were ['spam', 'eggs', 'ham']. But this function "
        "assumes labels are ordered lexicographically. "
        "Pass the ordered labels=['eggs', 'ham', 'spam'] and ensure that "
        "the columns of y_prob correspond to this ordering."
    )
    with pytest.warns(UserWarning, match=expected_message):
        brier_score_loss(
            ["eggs", "spam", "ham"],
            [
                [1, 0, 0],
                [0, 1, 0],
                [0, 0, 1],
            ],
            labels=["spam", "eggs", "ham"],
        )


def test_balanced_accuracy_score_unseen():
    msg = "y_pred contains classes not in y_true"
    with pytest.warns(UserWarning, match=msg):
        balanced_accuracy_score([0, 0, 0], [0, 0, 1])


@pytest.mark.parametrize(
    "y_true,y_pred",
    [
        (["a", "b", "a", "b"], ["a", "a", "a", "b"]),
        (["a", "b", "c", "b"], ["a", "a", "a", "b"]),
        (["a", "a", "a", "b"], ["a", "b", "c", "b"]),
    ],
)
def test_balanced_accuracy_score(y_true, y_pred):
    macro_recall = recall_score(
        y_true, y_pred, average="macro", labels=np.unique(y_true)
    )
    with ignore_warnings():
        # Warnings are tested in test_balanced_accuracy_score_unseen
        balanced = balanced_accuracy_score(y_true, y_pred)
    assert balanced == pytest.approx(macro_recall)
    adjusted = balanced_accuracy_score(y_true, y_pred, adjusted=True)
    chance = balanced_accuracy_score(y_true, np.full_like(y_true, y_true[0]))
    assert adjusted == (balanced - chance) / (1 - chance)


@pytest.mark.parametrize(
    "metric",
    [
        jaccard_score,
        f1_score,
        partial(fbeta_score, beta=0.5),
        precision_recall_fscore_support,
        precision_score,
        recall_score,
        brier_score_loss,
    ],
)
@pytest.mark.parametrize(
    "classes", [(False, True), (0, 1), (0.0, 1.0), ("zero", "one")]
)
def test_classification_metric_pos_label_types(metric, classes):
    """Check that the metric works with different types of `pos_label`.

    We can expect `pos_label` to be a bool, an integer, a float, a string.
    No error should be raised for those types.
    """
    rng = np.random.RandomState(42)
    n_samples, pos_label = 10, classes[-1]
    y_true = rng.choice(classes, size=n_samples, replace=True)
    if metric is brier_score_loss:
        # brier score loss requires probabilities
        y_pred = rng.uniform(size=n_samples)
    else:
        y_pred = y_true.copy()
    result = metric(y_true, y_pred, pos_label=pos_label)
    assert not np.any(np.isnan(result))


@pytest.mark.parametrize(
    "y_true, y_pred, expected_score",
    [
        (np.array([0, 1]), np.array([1, 0]), 0.0),
        (np.array([0, 1]), np.array([0, 1]), 1.0),
        (np.array([0, 1]), np.array([0, 0]), 0.0),
        (np.array([0, 0]), np.array([0, 0]), 1.0),
    ],
)
def test_f1_for_small_binary_inputs_with_zero_division(y_true, y_pred, expected_score):
    """Check the behaviour of `zero_division` for f1-score.

    Non-regression test for:
    https://github.com/scikit-learn/scikit-learn/issues/26965
    """
    assert f1_score(y_true, y_pred, zero_division=1.0) == pytest.approx(expected_score)


@pytest.mark.parametrize(
    "scoring",
    [
        make_scorer(f1_score, zero_division=np.nan),
        make_scorer(fbeta_score, beta=2, zero_division=np.nan),
        make_scorer(precision_score, zero_division=np.nan),
        make_scorer(recall_score, zero_division=np.nan),
    ],
)
def test_classification_metric_division_by_zero_nan_validaton(scoring):
    """Check that we validate `np.nan` properly for classification metrics.

    With `n_jobs=2` in cross-validation, the `np.nan` used for the singleton will be
    different in the sub-process and we should not use the `is` operator but
    `math.isnan`.

    Non-regression test for:
    https://github.com/scikit-learn/scikit-learn/issues/27563
    """
    X, y = datasets.make_classification(random_state=0)
    classifier = DecisionTreeClassifier(max_depth=3, random_state=0).fit(X, y)
    cross_val_score(classifier, X, y, scoring=scoring, n_jobs=2, error_score="raise")


def test_d2_log_loss_score():
    y_true = [0, 0, 0, 1, 1, 1]
    y_true_string = ["no", "no", "no", "yes", "yes", "yes"]
    y_pred = np.array(
        [
            [0.5, 0.5],
            [0.9, 0.1],
            [0.4, 0.6],
            [0.6, 0.4],
            [0.35, 0.65],
            [0.01, 0.99],
        ]
    )
    y_pred_null = np.array(
        [
            [0.5, 0.5],
            [0.5, 0.5],
            [0.5, 0.5],
            [0.5, 0.5],
            [0.5, 0.5],
            [0.5, 0.5],
        ]
    )
    d2_score = d2_log_loss_score(y_true=y_true, y_pred=y_pred)
    log_likelihood = log_loss(y_true=y_true, y_pred=y_pred, normalize=False)
    log_likelihood_null = log_loss(y_true=y_true, y_pred=y_pred_null, normalize=False)
    d2_score_true = 1 - log_likelihood / log_likelihood_null
    assert d2_score == pytest.approx(d2_score_true)

    # check that using sample weight also gives the correct d2 score
    sample_weight = np.array([2, 1, 3, 4, 3, 1])
    y_pred_null[:, 0] = sample_weight[:3].sum() / sample_weight.sum()
    y_pred_null[:, 1] = sample_weight[3:].sum() / sample_weight.sum()
    d2_score = d2_log_loss_score(
        y_true=y_true, y_pred=y_pred, sample_weight=sample_weight
    )
    log_likelihood = log_loss(
        y_true=y_true,
        y_pred=y_pred,
        sample_weight=sample_weight,
        normalize=False,
    )
    log_likelihood_null = log_loss(
        y_true=y_true,
        y_pred=y_pred_null,
        sample_weight=sample_weight,
        normalize=False,
    )
    d2_score_true = 1 - log_likelihood / log_likelihood_null
    assert d2_score == pytest.approx(d2_score_true)

    # check if good predictions give a relatively higher value for the d2 score
    y_pred = np.array(
        [
            [0.9, 0.1],
            [0.8, 0.2],
            [0.9, 0.1],
            [0.1, 0.9],
            [0.2, 0.8],
            [0.1, 0.9],
        ]
    )
    d2_score = d2_log_loss_score(y_true, y_pred)
    assert 0.5 < d2_score < 1.0
    # check that a similar value is obtained for string labels
    d2_score_string = d2_log_loss_score(y_true_string, y_pred)
    assert d2_score_string == pytest.approx(d2_score)

    # check if poor predictions gives a relatively low value for the d2 score
    y_pred = np.array(
        [
            [0.5, 0.5],
            [0.1, 0.9],
            [0.1, 0.9],
            [0.9, 0.1],
            [0.75, 0.25],
            [0.1, 0.9],
        ]
    )
    d2_score = d2_log_loss_score(y_true, y_pred)
    assert d2_score < 0
    # check that a similar value is obtained for string labels
    d2_score_string = d2_log_loss_score(y_true_string, y_pred)
    assert d2_score_string == pytest.approx(d2_score)

    # check if simply using the average of the classes as the predictions
    # gives a d2 score of 0
    y_true = [0, 0, 0, 1, 1, 1]
    y_pred = np.array(
        [
            [0.5, 0.5],
            [0.5, 0.5],
            [0.5, 0.5],
            [0.5, 0.5],
            [0.5, 0.5],
            [0.5, 0.5],
        ]
    )
    d2_score = d2_log_loss_score(y_true, y_pred)
    assert d2_score == 0
    d2_score_string = d2_log_loss_score(y_true_string, y_pred)
    assert d2_score_string == 0

    # check if simply using the average of the classes as the predictions
    # gives a d2 score of 0 when the positive class has a higher proportion
    y_true = [0, 1, 1, 1]
    y_true_string = ["no", "yes", "yes", "yes"]
    y_pred = np.array([[0.25, 0.75], [0.25, 0.75], [0.25, 0.75], [0.25, 0.75]])
    d2_score = d2_log_loss_score(y_true, y_pred)
    assert d2_score == 0
    d2_score_string = d2_log_loss_score(y_true_string, y_pred)
    assert d2_score_string == 0
    sample_weight = [2, 2, 2, 2]
    d2_score_with_sample_weight = d2_log_loss_score(
        y_true, y_pred, sample_weight=sample_weight
    )
    assert d2_score_with_sample_weight == 0

    # check that the d2 scores seem correct when more than 2
    # labels are specified
    y_true = ["high", "high", "low", "neutral"]
    sample_weight = [1.4, 0.6, 0.8, 0.2]

    y_pred = np.array(
        [
            [0.8, 0.1, 0.1],
            [0.8, 0.1, 0.1],
            [0.1, 0.8, 0.1],
            [0.1, 0.1, 0.8],
        ]
    )
    d2_score = d2_log_loss_score(y_true, y_pred)
    assert 0.5 < d2_score < 1.0
    d2_score = d2_log_loss_score(y_true, y_pred, sample_weight=sample_weight)
    assert 0.5 < d2_score < 1.0

    y_pred = np.array(
        [
            [0.2, 0.5, 0.3],
            [0.1, 0.7, 0.2],
            [0.1, 0.1, 0.8],
            [0.2, 0.7, 0.1],
        ]
    )
    d2_score = d2_log_loss_score(y_true, y_pred)
    assert d2_score < 0
    d2_score = d2_log_loss_score(y_true, y_pred, sample_weight=sample_weight)
    assert d2_score < 0


def test_d2_log_loss_score_missing_labels():
    """Check that d2_log_loss_score works when not all labels are present in y_true

    non-regression test for https://github.com/scikit-learn/scikit-learn/issues/30713
    """
    y_true = [2, 0, 2, 0]
    labels = [0, 1, 2]
    sample_weight = [1.4, 0.6, 0.7, 0.3]
    y_pred = np.tile([1, 0, 0], (4, 1))

    log_loss_obs = log_loss(y_true, y_pred, sample_weight=sample_weight, labels=labels)

    # Null model consists of weighted average of the classes.
    # Given that the sum of the weights is 3,
    # - weighted average of 0s is (0.6 + 0.3) / 3 = 0.3
    # - weighted average of 1s is 0
    # - weighted average of 2s is (1.4 + 0.7) / 3 = 0.7
    y_pred_null = np.tile([0.3, 0, 0.7], (4, 1))
    log_loss_null = log_loss(
        y_true, y_pred_null, sample_weight=sample_weight, labels=labels
    )

    expected_d2_score = 1 - log_loss_obs / log_loss_null
    d2_score = d2_log_loss_score(
        y_true, y_pred, sample_weight=sample_weight, labels=labels
    )
    assert_allclose(d2_score, expected_d2_score)


def test_d2_log_loss_score_label_order():
    """Check that d2_log_loss_score doesn't depend on the order of the labels."""
    y_true = [2, 0, 2, 0]
    y_pred = np.tile([1, 0, 0], (4, 1))

    d2_score = d2_log_loss_score(y_true, y_pred, labels=[0, 1, 2])
    d2_score_other = d2_log_loss_score(y_true, y_pred, labels=[0, 2, 1])

    assert_allclose(d2_score, d2_score_other)


def test_d2_log_loss_score_raises():
    """Test that d2_log_loss_score raises the appropriate errors on
    invalid inputs."""
    y_true = [0, 1, 2]
    y_pred = [[0.2, 0.8], [0.5, 0.5], [0.4, 0.6]]
    err = "contain different number of classes"
    with pytest.raises(ValueError, match=err):
        d2_log_loss_score(y_true, y_pred)

    # check error if the number of classes in labels do not match the number
    # of classes in y_pred.
    y_true = [0, 1, 2]
    y_pred = [[0.5, 0.5], [0.5, 0.5], [0.5, 0.5]]
    labels = [0, 1, 2]
    err = "number of classes in labels is different"
    with pytest.raises(ValueError, match=err):
        d2_log_loss_score(y_true, y_pred, labels=labels)

    # check error if y_true and y_pred do not have equal lengths
    y_true = [0, 1, 2]
    y_pred = [[0.5, 0.5, 0.5], [0.6, 0.3, 0.1]]
    err = "inconsistent numbers of samples"
    with pytest.raises(ValueError, match=err):
        d2_log_loss_score(y_true, y_pred)

    # check warning for samples < 2
    y_true = [1]
    y_pred = [[0.5, 0.5]]
    err = "score is not well-defined"
    with pytest.warns(UndefinedMetricWarning, match=err):
        d2_log_loss_score(y_true, y_pred)

    # check error when y_true only has 1 label
    y_true = [1, 1, 1]
    y_pred = [[0.5, 0.5], [0.5, 0.5], [0.5, 0.5]]
    err = "y_true contains only one label"
    with pytest.raises(ValueError, match=err):
        d2_log_loss_score(y_true, y_pred)

    # check error when y_true only has 1 label and labels also has
    # only 1 label
    y_true = [1, 1, 1]
    labels = [1]
    y_pred = [[0.5, 0.5], [0.5, 0.5], [0.5, 0.5]]
    err = "The labels array needs to contain at least two"
    with pytest.raises(ValueError, match=err):
        d2_log_loss_score(y_true, y_pred, labels=labels)
