group-wbl/.venv/lib/python3.13/site-packages/sklearn/utils/tests/test_stats.py

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2026-01-09 09:48:03 +08:00
import numpy as np
import pytest
from numpy.testing import assert_allclose, assert_array_equal
from pytest import approx
from sklearn._config import config_context
from sklearn.utils._array_api import (
_convert_to_numpy,
get_namespace,
yield_namespace_device_dtype_combinations,
)
from sklearn.utils._array_api import device as array_device
from sklearn.utils.estimator_checks import _array_api_for_tests
from sklearn.utils.fixes import np_version, parse_version
from sklearn.utils.stats import _weighted_percentile
@pytest.mark.parametrize("average", [True, False])
@pytest.mark.parametrize("size", [10, 15])
def test_weighted_percentile_matches_median(size, average):
"""Ensure `_weighted_percentile` matches `median` when expected.
With unit `sample_weight`, `_weighted_percentile` should match the median except
when `average=False` and the number of samples is even.
For an even array and `average=False`, `percentile_rank=50` gives the lower
of the two 'middle' values, that are averaged when calculating the `median`.
"""
y = np.arange(size)
sample_weight = np.ones_like(y)
score = _weighted_percentile(y, sample_weight, 50, average=average)
# `_weighted_percentile(average=False)` does not match `median` when n is even
if size % 2 == 0 and average is False:
assert score != np.median(y)
else:
assert approx(score) == np.median(y)
@pytest.mark.parametrize("average", [True, False])
@pytest.mark.parametrize("percentile_rank", [20, 35, 61, [5, 47]])
@pytest.mark.parametrize("size", [10, 15])
def test_weighted_percentile_matches_numpy(
global_random_seed, size, percentile_rank, average
):
"""Check `_weighted_percentile` with unit weights is correct.
`average=True` results should be the same as `np.percentile`'s
'averaged_inverted_cdf'.
`average=False` results should be the same as `np.percentile`'s
'inverted_cdf'.
Note `np.percentile` is the same as `np.quantile` except `q` is in range [0, 100].
We parametrize through different `percentile_rank` and `size` to
ensure we get cases where `g=0` and `g>0` (see Hyndman and Fan 1996 for details).
"""
rng = np.random.RandomState(global_random_seed)
y = rng.randint(20, size=size)
sw = np.ones_like(y)
score = _weighted_percentile(y, sw, percentile_rank, average=average)
if average:
method = "averaged_inverted_cdf"
else:
method = "inverted_cdf"
assert approx(score) == np.percentile(y, percentile_rank, method=method)
@pytest.mark.parametrize("percentile_rank", [50, 100])
def test_weighted_percentile_plus_one_clip_max(percentile_rank):
"""Check `j+1` index is clipped to max, when `average=True`.
`percentile_plus_one_indices` can exceed max index when `percentile_indices`
is already at max index.
Note that when `g` (Hyndman and Fan) / `fraction_above` is greater than 0,
`j+1` (Hyndman and Fan) / `percentile_plus_one_indices` is calculated but
never used, so it does not matter what this value is.
When percentile of percentile rank 100 falls exactly on the last value in the
`weighted_cdf`, `g=0` and `percentile_indices` is at max index. In this case
we set `percentile_plus_one_indices` to be max index as well, so the result is
the average of 2x the max index (i.e. last value of `weighted_cdf`).
"""
# Note for both `percentile_rank`s 50 and 100,`percentile_indices` is already at
# max index
y = np.array([[0, 0], [1, 1]])
sw = np.array([[0.1, 0.2], [2, 3]])
score = _weighted_percentile(y, sw, percentile_rank, average=True)
for idx in range(2):
assert score[idx] == approx(1.0)
def test_weighted_percentile_equal():
"""Check `weighted_percentile` with unit weights and all 0 values in `array`."""
y = np.zeros(102, dtype=np.float64)
sw = np.ones(102, dtype=np.float64)
score = _weighted_percentile(y, sw, 50)
assert approx(score) == 0
# XXX: is this really what we want? Shouldn't we raise instead?
# https://github.com/scikit-learn/scikit-learn/issues/31032
def test_weighted_percentile_all_zero_weights():
"""Check `weighted_percentile` with all weights equal to 0 returns last index."""
y = np.arange(10)
sw = np.zeros(10)
value = _weighted_percentile(y, sw, 50)
assert approx(value) == 9.0
@pytest.mark.parametrize("average", [True, False])
@pytest.mark.parametrize("percentile_rank, expected_value", [(0, 2), (50, 3), (100, 5)])
def test_weighted_percentile_ignores_zero_weight(
average, percentile_rank, expected_value
):
"""Check leading, trailing and middle 0 weights behave correctly.
Check that leading zero-weight observations are ignored when `percentile_rank=0`.
See #20528 for details.
Check that when `average=True` and the `j+1` ('plus one') index has sample weight
of 0, it is ignored. Also check that trailing zero weight observations are ignored
(e.g., when `percentile_rank=100`).
"""
y = np.array([0, 1, 2, 3, 4, 5, 6])
sw = np.array([0, 0, 1, 1, 0, 1, 0])
value = _weighted_percentile(
np.vstack((y, y)).T, np.vstack((sw, sw)).T, percentile_rank, average=average
)
for idx in range(2):
assert approx(value[idx]) == expected_value
@pytest.mark.parametrize("average", [True, False])
@pytest.mark.parametrize("percentile_rank", [20, 35, 50, 61])
def test_weighted_percentile_frequency_weight_semantics(
global_random_seed, percentile_rank, average
):
"""Check integer weights give the same result as repeating values."""
rng = np.random.RandomState(global_random_seed)
x = rng.randint(20, size=10)
weights = rng.choice(5, size=10)
x_repeated = np.repeat(x, weights)
percentile_weights = _weighted_percentile(
x, weights, percentile_rank, average=average
)
percentile_repeated = _weighted_percentile(
x_repeated, np.ones_like(x_repeated), percentile_rank, average=average
)
assert percentile_weights == approx(percentile_repeated)
# Also check `percentile_rank=50` matches `median`
if percentile_rank == 50 and average:
assert percentile_weights == approx(np.median(x_repeated))
@pytest.mark.parametrize("constant", [5, 8])
@pytest.mark.parametrize("average", [True, False])
@pytest.mark.parametrize("percentile_rank", [20, 35, 50, 61, [20, 35, 50, 61]])
def test_weighted_percentile_constant_multiplier(
global_random_seed, percentile_rank, average, constant
):
"""Check multiplying weights by a constant does not change the result.
Note scale invariance does not always hold when multiplying by a
float due to cumulative sum numerical error (which grows proportional to n).
"""
rng = np.random.RandomState(global_random_seed)
x = rng.randint(20, size=20)
weights = rng.choice(5, size=20)
weights_multiplied = weights * constant
percentile = _weighted_percentile(x, weights, percentile_rank, average=average)
percentile_multiplier = _weighted_percentile(
x, weights_multiplied, percentile_rank, average=average
)
assert percentile == approx(percentile_multiplier)
@pytest.mark.parametrize("percentile_rank", [50, [20, 35, 50]])
@pytest.mark.parametrize("average", [True, False])
def test_weighted_percentile_2d(global_random_seed, percentile_rank, average):
"""Check `_weighted_percentile` behaviour is correct when `array` is 2D."""
# Check for when array 2D and sample_weight 1D
rng = np.random.RandomState(global_random_seed)
x1 = rng.randint(10, size=10)
w1 = rng.choice(5, size=10)
x2 = rng.randint(20, size=10)
x_2d = np.vstack((x1, x2)).T
wp = _weighted_percentile(
x_2d, w1, percentile_rank=percentile_rank, average=average
)
if isinstance(percentile_rank, list):
p_list = []
for pr in percentile_rank:
p_list.append(
[
_weighted_percentile(
x_2d[:, i], w1, percentile_rank=pr, average=average
)
for i in range(x_2d.shape[1])
]
)
p_axis_0 = np.stack(p_list, axis=-1)
assert wp.shape == (x_2d.shape[1], len(percentile_rank))
else:
# percentile_rank is scalar
p_axis_0 = [
_weighted_percentile(
x_2d[:, i], w1, percentile_rank=percentile_rank, average=average
)
for i in range(x_2d.shape[1])
]
assert wp.shape == (x_2d.shape[1],)
assert_allclose(wp, p_axis_0)
# Check when array and sample_weight both 2D
w2 = rng.choice(5, size=10)
w_2d = np.vstack((w1, w2)).T
wp = _weighted_percentile(
x_2d, w_2d, percentile_rank=percentile_rank, average=average
)
if isinstance(percentile_rank, list):
p_list = []
for pr in percentile_rank:
p_list.append(
[
_weighted_percentile(
x_2d[:, i], w_2d[:, i], percentile_rank=pr, average=average
)
for i in range(x_2d.shape[1])
]
)
p_axis_0 = np.stack(p_list, axis=-1)
assert wp.shape == (x_2d.shape[1], len(percentile_rank))
else:
# percentile_rank is scalar
p_axis_0 = [
_weighted_percentile(
x_2d[:, i], w_2d[:, i], percentile_rank=percentile_rank, average=average
)
for i in range(x_2d.shape[1])
]
assert wp.shape == (x_2d.shape[1],)
assert_allclose(wp, p_axis_0)
@pytest.mark.parametrize(
"array_namespace, device, dtype_name", yield_namespace_device_dtype_combinations()
)
@pytest.mark.parametrize(
"data, weights, percentile",
[
# NumPy scalars input (handled as 0D arrays on array API)
(np.float32(42), np.int32(1), 50),
# Random 1D array, constant weights
(lambda rng: rng.rand(50), np.ones(50).astype(np.int32), 50),
# Random 2D array and random 1D weights
(lambda rng: rng.rand(50, 3), lambda rng: rng.rand(50).astype(np.float32), 75),
# Random 2D array and random 2D weights
(
lambda rng: rng.rand(20, 3),
lambda rng: rng.rand(20, 3).astype(np.float32),
[25, 75],
),
# zero-weights and `rank_percentile=0` (#20528) (`sample_weight` dtype: int64)
(np.array([0, 1, 2, 3, 4, 5]), np.array([0, 0, 1, 1, 1, 0]), 0),
# np.nan's in data and some zero-weights (`sample_weight` dtype: int64)
(np.array([np.nan, np.nan, 0, 3, 4, 5]), np.array([0, 1, 1, 1, 1, 0]), 0),
# `sample_weight` dtype: int32
(
np.array([0, 1, 2, 3, 4, 5]),
np.array([0, 1, 1, 1, 1, 0], dtype=np.int32),
[25, 75],
),
],
)
def test_weighted_percentile_array_api_consistency(
global_random_seed, array_namespace, device, dtype_name, data, weights, percentile
):
"""Check `_weighted_percentile` gives consistent results with array API."""
xp = _array_api_for_tests(array_namespace, device)
# Skip test for percentile=0 edge case (#20528) on namespace/device where
# xp.nextafter is broken. This is the case for torch with MPS device:
# https://github.com/pytorch/pytorch/issues/150027
zero = xp.zeros(1, device=device)
one = xp.ones(1, device=device)
if percentile == 0 and xp.all(xp.nextafter(zero, one) == zero):
pytest.xfail(f"xp.nextafter is broken on {device}")
rng = np.random.RandomState(global_random_seed)
X_np = data(rng) if callable(data) else data
weights_np = weights(rng) if callable(weights) else weights
# Ensure `data` of correct dtype
X_np = X_np.astype(dtype_name)
result_np = _weighted_percentile(X_np, weights_np, percentile)
# Convert to Array API arrays
X_xp = xp.asarray(X_np, device=device)
weights_xp = xp.asarray(weights_np, device=device)
with config_context(array_api_dispatch=True):
result_xp = _weighted_percentile(X_xp, weights_xp, percentile)
assert array_device(result_xp) == array_device(X_xp)
assert get_namespace(result_xp)[0] == get_namespace(X_xp)[0]
result_xp_np = _convert_to_numpy(result_xp, xp=xp)
assert result_xp_np.dtype == result_np.dtype
assert result_xp_np.shape == result_np.shape
assert_allclose(result_np, result_xp_np)
# Check dtype correct (`sample_weight` should follow `array`)
if dtype_name == "float32":
assert result_xp_np.dtype == result_np.dtype == np.float32
else:
assert result_xp_np.dtype == np.float64
@pytest.mark.parametrize("average", [True, False])
@pytest.mark.parametrize("sample_weight_ndim", [1, 2])
def test_weighted_percentile_nan_filtered(
global_random_seed, sample_weight_ndim, average
):
"""Test `_weighted_percentile` ignores NaNs.
Calling `_weighted_percentile` on an array with nan values returns the same
results as calling `_weighted_percentile` on a filtered version of the data.
We test both with sample_weight of the same shape as the data and with
one-dimensional sample_weight.
"""
rng = np.random.RandomState(global_random_seed)
array_with_nans = rng.rand(100, 10)
array_with_nans[rng.rand(*array_with_nans.shape) < 0.5] = np.nan
nan_mask = np.isnan(array_with_nans)
if sample_weight_ndim == 2:
sample_weight = rng.randint(1, 6, size=(100, 10))
else:
sample_weight = rng.randint(1, 6, size=(100,))
# Find the weighted percentile on the array with nans:
results = _weighted_percentile(array_with_nans, sample_weight, 30, average=average)
# Find the weighted percentile on the filtered array:
filtered_array = [
array_with_nans[~nan_mask[:, col], col]
for col in range(array_with_nans.shape[1])
]
if sample_weight.ndim == 1:
sample_weight = np.repeat(sample_weight, array_with_nans.shape[1]).reshape(
array_with_nans.shape[0], array_with_nans.shape[1]
)
filtered_weights = [
sample_weight[~nan_mask[:, col], col] for col in range(array_with_nans.shape[1])
]
expected_results = np.array(
[
_weighted_percentile(
filtered_array[col], filtered_weights[col], 30, average=average
)
for col in range(array_with_nans.shape[1])
]
)
assert_array_equal(expected_results, results)
@pytest.mark.parametrize(
"percentile_rank, expected",
[
(90, [np.nan, 5]),
([50, 90], [[np.nan, np.nan], [2.0, 5.0]]),
],
)
def test_weighted_percentile_all_nan_column(percentile_rank, expected):
"""Check that nans are ignored in general, except for all NaN columns."""
array = np.array(
[
[np.nan, 5],
[np.nan, 1],
[np.nan, np.nan],
[np.nan, np.nan],
[np.nan, 2],
[np.nan, np.nan],
]
)
weights = np.ones_like(array)
values = _weighted_percentile(array, weights, percentile_rank)
# The percentile of the second column should be `5` even though there are many nan
# values present; the percentile of the first column can only be nan, since there
# are no other possible values:
assert np.array_equal(values, expected, equal_nan=True)
@pytest.mark.skipif(
np_version < parse_version("2.0"),
reason="np.quantile only accepts weights since version 2.0",
)
@pytest.mark.parametrize("percentile", [66, 10, 50])
@pytest.mark.parametrize("average", [False, True])
@pytest.mark.parametrize("uniform_weight", [False, True])
def test_weighted_percentile_like_numpy_quantile(
percentile, average, uniform_weight, global_random_seed
):
"""Check `_weighted_percentile` is equivalent to `np.quantile` with weights."""
# TODO: remove the following skip once no longer applicable.
if average and not uniform_weight:
pytest.skip(
"np.quantile does not support weights with method='averaged_inverted_cdf'"
)
rng = np.random.RandomState(global_random_seed)
array = rng.rand(10, 100)
if uniform_weight:
sample_weight = np.ones_like(array) * rng.randint(1, 6, size=1)
else:
sample_weight = rng.randint(1, 6, size=(10, 100))
percentile_weighted_percentile = _weighted_percentile(
array, sample_weight, percentile, average=average
)
percentile_numpy_quantile = np.quantile(
array,
percentile / 100,
weights=sample_weight if not uniform_weight else None,
method="averaged_inverted_cdf" if average else "inverted_cdf",
axis=0,
)
assert_array_equal(percentile_weighted_percentile, percentile_numpy_quantile)
@pytest.mark.skipif(
np_version < parse_version("2.0"),
reason="np.nanquantile only accepts weights since version 2.0",
)
@pytest.mark.parametrize("percentile", [66, 10, 50])
@pytest.mark.parametrize("average", [False, True])
@pytest.mark.parametrize("uniform_weight", [False, True])
def test_weighted_percentile_like_numpy_nanquantile(
percentile, average, uniform_weight, global_random_seed
):
"""Check `_weighted_percentile` equivalent to `np.nanquantile` with weights."""
# TODO: remove the following skip once no longer applicable.
if average and not uniform_weight:
pytest.skip(
"np.nanquantile does not support weights with "
"method='averaged_inverted_cdf'"
)
rng = np.random.RandomState(global_random_seed)
array_with_nans = rng.rand(10, 100)
array_with_nans[rng.rand(*array_with_nans.shape) < 0.5] = np.nan
if uniform_weight:
sample_weight = np.ones_like(array_with_nans) * rng.randint(
1,
6,
size=1,
)
else:
sample_weight = rng.randint(1, 6, size=(10, 100))
percentile_weighted_percentile = _weighted_percentile(
array_with_nans, sample_weight, percentile, average=average
)
percentile_numpy_nanquantile = np.nanquantile(
array_with_nans,
percentile / 100,
weights=sample_weight if not uniform_weight else None,
method="averaged_inverted_cdf" if average else "inverted_cdf",
axis=0,
)
assert_array_equal(percentile_weighted_percentile, percentile_numpy_nanquantile)