"""
Basic statistics module.

This module provides functions for calculating statistics of data, including
averages, variance, and standard deviation.

Calculating averages
--------------------

==================  ==================================================
Function            Description
==================  ==================================================
mean                Arithmetic mean (average) of data.
fmean               Fast, floating-point arithmetic mean.
geometric_mean      Geometric mean of data.
harmonic_mean       Harmonic mean of data.
median              Median (middle value) of data.
median_low          Low median of data.
median_high         High median of data.
median_grouped      Median, or 50th percentile, of grouped data.
mode                Mode (most common value) of data.
multimode           List of modes (most common values of data).
quantiles           Divide data into intervals with equal probability.
==================  ==================================================

Calculate the arithmetic mean ("the average") of data:

>>> mean([-1.0, 2.5, 3.25, 5.75])
2.625


Calculate the standard median of discrete data:

>>> median([2, 3, 4, 5])
3.5


Calculate the median, or 50th percentile, of data grouped into class intervals
centred on the data values provided. E.g. if your data points are rounded to
the nearest whole number:

>>> median_grouped([2, 2, 3, 3, 3, 4])  #doctest: +ELLIPSIS
2.8333333333...

This should be interpreted in this way: you have two data points in the class
interval 1.5-2.5, three data points in the class interval 2.5-3.5, and one in
the class interval 3.5-4.5. The median of these data points is 2.8333...


Calculating variability or spread
---------------------------------

==================  =============================================
Function            Description
==================  =============================================
pvariance           Population variance of data.
variance            Sample variance of data.
pstdev              Population standard deviation of data.
stdev               Sample standard deviation of data.
==================  =============================================

Calculate the standard deviation of sample data:

>>> stdev([2.5, 3.25, 5.5, 11.25, 11.75])  #doctest: +ELLIPSIS
4.38961843444...

If you have previously calculated the mean, you can pass it as the optional
second argument to the four "spread" functions to avoid recalculating it:

>>> data = [1, 2, 2, 4, 4, 4, 5, 6]
>>> mu = mean(data)
>>> pvariance(data, mu)
2.5


Statistics for relations between two inputs
-------------------------------------------

==================  ====================================================
Function            Description
==================  ====================================================
covariance          Sample covariance for two variables.
correlation         Pearson's correlation coefficient for two variables.
linear_regression   Intercept and slope for simple linear regression.
==================  ====================================================

Calculate covariance, Pearson's correlation, and simple linear regression
for two inputs:

>>> x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> y = [1, 2, 3, 1, 2, 3, 1, 2, 3]
>>> covariance(x, y)
0.75
>>> correlation(x, y)  #doctest: +ELLIPSIS
0.31622776601...
>>> linear_regression(x, y)  #doctest:
LinearRegression(slope=0.1, intercept=1.5)


Exceptions
----------

A single exception is defined: StatisticsError is a subclass of ValueError.

"""

import sys
from _typeshed import SupportsRichComparisonT
from collections.abc import Callable, Hashable, Iterable, Sequence, Sized
from decimal import Decimal
from fractions import Fraction
from typing import Literal, NamedTuple, Protocol, SupportsFloat, SupportsIndex, TypeVar, type_check_only
from typing_extensions import Self, TypeAlias

__all__ = [
    "StatisticsError",
    "fmean",
    "geometric_mean",
    "mean",
    "harmonic_mean",
    "pstdev",
    "pvariance",
    "stdev",
    "variance",
    "median",
    "median_low",
    "median_high",
    "median_grouped",
    "mode",
    "multimode",
    "NormalDist",
    "quantiles",
]

if sys.version_info >= (3, 10):
    __all__ += ["covariance", "correlation", "linear_regression"]
if sys.version_info >= (3, 13):
    __all__ += ["kde", "kde_random"]

# Most functions in this module accept homogeneous collections of one of these types
_Number: TypeAlias = float | Decimal | Fraction
_NumberT = TypeVar("_NumberT", float, Decimal, Fraction)

# Used in mode, multimode
_HashableT = TypeVar("_HashableT", bound=Hashable)

# Used in NormalDist.samples and kde_random
_Seed: TypeAlias = int | float | str | bytes | bytearray  # noqa: Y041

# Used in linear_regression
_T_co = TypeVar("_T_co", covariant=True)

@type_check_only
class _SizedIterable(Iterable[_T_co], Sized, Protocol[_T_co]): ...

class StatisticsError(ValueError): ...

if sys.version_info >= (3, 11):
    def fmean(data: Iterable[SupportsFloat], weights: Iterable[SupportsFloat] | None = None) -> float:
        """Convert data to floats and compute the arithmetic mean.

        This runs faster than the mean() function and it always returns a float.
        If the input dataset is empty, it raises a StatisticsError.

        >>> fmean([3.5, 4.0, 5.25])
        4.25

        """

else:
    def fmean(data: Iterable[SupportsFloat]) -> float:
        """Convert data to floats and compute the arithmetic mean.

        This runs faster than the mean() function and it always returns a float.
        If the input dataset is empty, it raises a StatisticsError.

        >>> fmean([3.5, 4.0, 5.25])
        4.25
        """

def geometric_mean(data: Iterable[SupportsFloat]) -> float:
    """Convert data to floats and compute the geometric mean.

    Raises a StatisticsError if the input dataset is empty
    or if it contains a negative value.

    Returns zero if the product of inputs is zero.

    No special efforts are made to achieve exact results.
    (However, this may change in the future.)

    >>> round(geometric_mean([54, 24, 36]), 9)
    36.0

    """

def mean(data: Iterable[_NumberT]) -> _NumberT:
    """Return the sample arithmetic mean of data.

    >>> mean([1, 2, 3, 4, 4])
    2.8

    >>> from fractions import Fraction as F
    >>> mean([F(3, 7), F(1, 21), F(5, 3), F(1, 3)])
    Fraction(13, 21)

    >>> from decimal import Decimal as D
    >>> mean([D("0.5"), D("0.75"), D("0.625"), D("0.375")])
    Decimal('0.5625')

    If ``data`` is empty, StatisticsError will be raised.

    """

if sys.version_info >= (3, 10):
    def harmonic_mean(data: Iterable[_NumberT], weights: Iterable[_Number] | None = None) -> _NumberT:
        """Return the harmonic mean of data.

        The harmonic mean is the reciprocal of the arithmetic mean of the
        reciprocals of the data.  It can be used for averaging ratios or
        rates, for example speeds.

        Suppose a car travels 40 km/hr for 5 km and then speeds-up to
        60 km/hr for another 5 km. What is the average speed?

            >>> harmonic_mean([40, 60])
            48.0

        Suppose a car travels 40 km/hr for 5 km, and when traffic clears,
        speeds-up to 60 km/hr for the remaining 30 km of the journey. What
        is the average speed?

            >>> harmonic_mean([40, 60], weights=[5, 30])
            56.0

        If ``data`` is empty, or any element is less than zero,
        ``harmonic_mean`` will raise ``StatisticsError``.

        """

else:
    def harmonic_mean(data: Iterable[_NumberT]) -> _NumberT:
        """Return the harmonic mean of data.

        The harmonic mean, sometimes called the subcontrary mean, is the
        reciprocal of the arithmetic mean of the reciprocals of the data,
        and is often appropriate when averaging quantities which are rates
        or ratios, for example speeds. Example:

        Suppose an investor purchases an equal value of shares in each of
        three companies, with P/E (price/earning) ratios of 2.5, 3 and 10.
        What is the average P/E ratio for the investor's portfolio?

        >>> harmonic_mean([2.5, 3, 10])  # For an equal investment portfolio.
        3.6

        Using the arithmetic mean would give an average of about 5.167, which
        is too high.

        If ``data`` is empty, or any element is less than zero,
        ``harmonic_mean`` will raise ``StatisticsError``.
        """

def median(data: Iterable[_NumberT]) -> _NumberT:
    """Return the median (middle value) of numeric data.

    When the number of data points is odd, return the middle data point.
    When the number of data points is even, the median is interpolated by
    taking the average of the two middle values:

    >>> median([1, 3, 5])
    3
    >>> median([1, 3, 5, 7])
    4.0

    """

def median_low(data: Iterable[SupportsRichComparisonT]) -> SupportsRichComparisonT:
    """Return the low median of numeric data.

    When the number of data points is odd, the middle value is returned.
    When it is even, the smaller of the two middle values is returned.

    >>> median_low([1, 3, 5])
    3
    >>> median_low([1, 3, 5, 7])
    3

    """

def median_high(data: Iterable[SupportsRichComparisonT]) -> SupportsRichComparisonT:
    """Return the high median of data.

    When the number of data points is odd, the middle value is returned.
    When it is even, the larger of the two middle values is returned.

    >>> median_high([1, 3, 5])
    3
    >>> median_high([1, 3, 5, 7])
    5

    """

if sys.version_info >= (3, 11):
    def median_grouped(data: Iterable[SupportsFloat], interval: SupportsFloat = 1.0) -> float:
        """Estimates the median for numeric data binned around the midpoints
        of consecutive, fixed-width intervals.

        The *data* can be any iterable of numeric data with each value being
        exactly the midpoint of a bin.  At least one value must be present.

        The *interval* is width of each bin.

        For example, demographic information may have been summarized into
        consecutive ten-year age groups with each group being represented
        by the 5-year midpoints of the intervals:

            >>> demographics = Counter({
            ...    25: 172,   # 20 to 30 years old
            ...    35: 484,   # 30 to 40 years old
            ...    45: 387,   # 40 to 50 years old
            ...    55:  22,   # 50 to 60 years old
            ...    65:   6,   # 60 to 70 years old
            ... })

        The 50th percentile (median) is the 536th person out of the 1071
        member cohort.  That person is in the 30 to 40 year old age group.

        The regular median() function would assume that everyone in the
        tricenarian age group was exactly 35 years old.  A more tenable
        assumption is that the 484 members of that age group are evenly
        distributed between 30 and 40.  For that, we use median_grouped().

            >>> data = list(demographics.elements())
            >>> median(data)
            35
            >>> round(median_grouped(data, interval=10), 1)
            37.5

        The caller is responsible for making sure the data points are separated
        by exact multiples of *interval*.  This is essential for getting a
        correct result.  The function does not check this precondition.

        Inputs may be any numeric type that can be coerced to a float during
        the interpolation step.

        """

else:
    def median_grouped(data: Iterable[_NumberT], interval: _NumberT | float = 1) -> _NumberT | float:
        """Return the 50th percentile (median) of grouped continuous data.

        >>> median_grouped([1, 2, 2, 3, 4, 4, 4, 4, 4, 5])
        3.7
        >>> median_grouped([52, 52, 53, 54])
        52.5

        This calculates the median as the 50th percentile, and should be
        used when your data is continuous and grouped. In the above example,
        the values 1, 2, 3, etc. actually represent the midpoint of classes
        0.5-1.5, 1.5-2.5, 2.5-3.5, etc. The middle value falls somewhere in
        class 3.5-4.5, and interpolation is used to estimate it.

        Optional argument ``interval`` represents the class interval, and
        defaults to 1. Changing the class interval naturally will change the
        interpolated 50th percentile value:

        >>> median_grouped([1, 3, 3, 5, 7], interval=1)
        3.25
        >>> median_grouped([1, 3, 3, 5, 7], interval=2)
        3.5

        This function does not check whether the data points are at least
        ``interval`` apart.
        """

def mode(data: Iterable[_HashableT]) -> _HashableT:
    """Return the most common data point from discrete or nominal data.

    ``mode`` assumes discrete data, and returns a single value. This is the
    standard treatment of the mode as commonly taught in schools:

        >>> mode([1, 1, 2, 3, 3, 3, 3, 4])
        3

    This also works with nominal (non-numeric) data:

        >>> mode(["red", "blue", "blue", "red", "green", "red", "red"])
        'red'

    If there are multiple modes with same frequency, return the first one
    encountered:

        >>> mode(['red', 'red', 'green', 'blue', 'blue'])
        'red'

    If *data* is empty, ``mode``, raises StatisticsError.

    """

def multimode(data: Iterable[_HashableT]) -> list[_HashableT]:
    """Return a list of the most frequently occurring values.

    Will return more than one result if there are multiple modes
    or an empty list if *data* is empty.

    >>> multimode('aabbbbbbbbcc')
    ['b']
    >>> multimode('aabbbbccddddeeffffgg')
    ['b', 'd', 'f']
    >>> multimode('')
    []

    """

def pstdev(data: Iterable[_NumberT], mu: _NumberT | None = None) -> _NumberT:
    """Return the square root of the population variance.

    See ``pvariance`` for arguments and other details.

    >>> pstdev([1.5, 2.5, 2.5, 2.75, 3.25, 4.75])
    0.986893273527251

    """

def pvariance(data: Iterable[_NumberT], mu: _NumberT | None = None) -> _NumberT:
    """Return the population variance of ``data``.

    data should be a sequence or iterable of Real-valued numbers, with at least one
    value. The optional argument mu, if given, should be the mean of
    the data. If it is missing or None, the mean is automatically calculated.

    Use this function to calculate the variance from the entire population.
    To estimate the variance from a sample, the ``variance`` function is
    usually a better choice.

    Examples:

    >>> data = [0.0, 0.25, 0.25, 1.25, 1.5, 1.75, 2.75, 3.25]
    >>> pvariance(data)
    1.25

    If you have already calculated the mean of the data, you can pass it as
    the optional second argument to avoid recalculating it:

    >>> mu = mean(data)
    >>> pvariance(data, mu)
    1.25

    Decimals and Fractions are supported:

    >>> from decimal import Decimal as D
    >>> pvariance([D("27.5"), D("30.25"), D("30.25"), D("34.5"), D("41.75")])
    Decimal('24.815')

    >>> from fractions import Fraction as F
    >>> pvariance([F(1, 4), F(5, 4), F(1, 2)])
    Fraction(13, 72)

    """

def quantiles(data: Iterable[_NumberT], *, n: int = 4, method: Literal["inclusive", "exclusive"] = "exclusive") -> list[_NumberT]:
    """Divide *data* into *n* continuous intervals with equal probability.

    Returns a list of (n - 1) cut points separating the intervals.

    Set *n* to 4 for quartiles (the default).  Set *n* to 10 for deciles.
    Set *n* to 100 for percentiles which gives the 99 cuts points that
    separate *data* in to 100 equal sized groups.

    The *data* can be any iterable containing sample.
    The cut points are linearly interpolated between data points.

    If *method* is set to *inclusive*, *data* is treated as population
    data.  The minimum value is treated as the 0th percentile and the
    maximum value is treated as the 100th percentile.

    """

def stdev(data: Iterable[_NumberT], xbar: _NumberT | None = None) -> _NumberT:
    """Return the square root of the sample variance.

    See ``variance`` for arguments and other details.

    >>> stdev([1.5, 2.5, 2.5, 2.75, 3.25, 4.75])
    1.0810874155219827

    """

def variance(data: Iterable[_NumberT], xbar: _NumberT | None = None) -> _NumberT:
    """Return the sample variance of data.

    data should be an iterable of Real-valued numbers, with at least two
    values. The optional argument xbar, if given, should be the mean of
    the data. If it is missing or None, the mean is automatically calculated.

    Use this function when your data is a sample from a population. To
    calculate the variance from the entire population, see ``pvariance``.

    Examples:

    >>> data = [2.75, 1.75, 1.25, 0.25, 0.5, 1.25, 3.5]
    >>> variance(data)
    1.3720238095238095

    If you have already calculated the mean of your data, you can pass it as
    the optional second argument ``xbar`` to avoid recalculating it:

    >>> m = mean(data)
    >>> variance(data, m)
    1.3720238095238095

    This function does not check that ``xbar`` is actually the mean of
    ``data``. Giving arbitrary values for ``xbar`` may lead to invalid or
    impossible results.

    Decimals and Fractions are supported:

    >>> from decimal import Decimal as D
    >>> variance([D("27.5"), D("30.25"), D("30.25"), D("34.5"), D("41.75")])
    Decimal('31.01875')

    >>> from fractions import Fraction as F
    >>> variance([F(1, 6), F(1, 2), F(5, 3)])
    Fraction(67, 108)

    """

class NormalDist:
    """Normal distribution of a random variable"""

    __slots__ = {"_mu": "Arithmetic mean of a normal distribution", "_sigma": "Standard deviation of a normal distribution"}
    def __init__(self, mu: float = 0.0, sigma: float = 1.0) -> None:
        """NormalDist where mu is the mean and sigma is the standard deviation."""

    @property
    def mean(self) -> float:
        """Arithmetic mean of the normal distribution."""

    @property
    def median(self) -> float:
        """Return the median of the normal distribution"""

    @property
    def mode(self) -> float:
        """Return the mode of the normal distribution

        The mode is the value x where which the probability density
        function (pdf) takes its maximum value.
        """

    @property
    def stdev(self) -> float:
        """Standard deviation of the normal distribution."""

    @property
    def variance(self) -> float:
        """Square of the standard deviation."""

    @classmethod
    def from_samples(cls, data: Iterable[SupportsFloat]) -> Self:
        """Make a normal distribution instance from sample data."""

    def samples(self, n: SupportsIndex, *, seed: _Seed | None = None) -> list[float]:
        """Generate *n* samples for a given mean and standard deviation."""

    def pdf(self, x: float) -> float:
        """Probability density function.  P(x <= X < x+dx) / dx"""

    def cdf(self, x: float) -> float:
        """Cumulative distribution function.  P(X <= x)"""

    def inv_cdf(self, p: float) -> float:
        """Inverse cumulative distribution function.  x : P(X <= x) = p

        Finds the value of the random variable such that the probability of
        the variable being less than or equal to that value equals the given
        probability.

        This function is also called the percent point function or quantile
        function.
        """

    def overlap(self, other: NormalDist) -> float:
        """Compute the overlapping coefficient (OVL) between two normal distributions.

        Measures the agreement between two normal probability distributions.
        Returns a value between 0.0 and 1.0 giving the overlapping area in
        the two underlying probability density functions.

            >>> N1 = NormalDist(2.4, 1.6)
            >>> N2 = NormalDist(3.2, 2.0)
            >>> N1.overlap(N2)
            0.8035050657330205
        """

    def quantiles(self, n: int = 4) -> list[float]:
        """Divide into *n* continuous intervals with equal probability.

        Returns a list of (n - 1) cut points separating the intervals.

        Set *n* to 4 for quartiles (the default).  Set *n* to 10 for deciles.
        Set *n* to 100 for percentiles which gives the 99 cuts points that
        separate the normal distribution in to 100 equal sized groups.
        """

    def zscore(self, x: float) -> float:
        """Compute the Standard Score.  (x - mean) / stdev

        Describes *x* in terms of the number of standard deviations
        above or below the mean of the normal distribution.
        """

    def __eq__(x1, x2: object) -> bool:
        """Two NormalDist objects are equal if their mu and sigma are both equal."""

    def __add__(x1, x2: float | NormalDist) -> NormalDist:
        """Add a constant or another NormalDist instance.

        If *other* is a constant, translate mu by the constant,
        leaving sigma unchanged.

        If *other* is a NormalDist, add both the means and the variances.
        Mathematically, this works only if the two distributions are
        independent or if they are jointly normally distributed.
        """

    def __sub__(x1, x2: float | NormalDist) -> NormalDist:
        """Subtract a constant or another NormalDist instance.

        If *other* is a constant, translate by the constant mu,
        leaving sigma unchanged.

        If *other* is a NormalDist, subtract the means and add the variances.
        Mathematically, this works only if the two distributions are
        independent or if they are jointly normally distributed.
        """

    def __mul__(x1, x2: float) -> NormalDist:
        """Multiply both mu and sigma by a constant.

        Used for rescaling, perhaps to change measurement units.
        Sigma is scaled with the absolute value of the constant.
        """

    def __truediv__(x1, x2: float) -> NormalDist:
        """Divide both mu and sigma by a constant.

        Used for rescaling, perhaps to change measurement units.
        Sigma is scaled with the absolute value of the constant.
        """

    def __pos__(x1) -> NormalDist:
        """Return a copy of the instance."""

    def __neg__(x1) -> NormalDist:
        """Negates mu while keeping sigma the same."""
    __radd__ = __add__
    def __rsub__(x1, x2: float | NormalDist) -> NormalDist:
        """Subtract a NormalDist from a constant or another NormalDist."""
    __rmul__ = __mul__
    def __hash__(self) -> int:
        """NormalDist objects hash equal if their mu and sigma are both equal."""

if sys.version_info >= (3, 12):
    def correlation(x: Sequence[_Number], y: Sequence[_Number], /, *, method: Literal["linear", "ranked"] = "linear") -> float:
        """Pearson's correlation coefficient

        Return the Pearson's correlation coefficient for two inputs. Pearson's
        correlation coefficient *r* takes values between -1 and +1. It measures
        the strength and direction of a linear relationship.

        >>> x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        >>> y = [9, 8, 7, 6, 5, 4, 3, 2, 1]
        >>> correlation(x, x)
        1.0
        >>> correlation(x, y)
        -1.0

        If *method* is "ranked", computes Spearman's rank correlation coefficient
        for two inputs.  The data is replaced by ranks.  Ties are averaged
        so that equal values receive the same rank.  The resulting coefficient
        measures the strength of a monotonic relationship.

        Spearman's rank correlation coefficient is appropriate for ordinal
        data or for continuous data that doesn't meet the linear proportion
        requirement for Pearson's correlation coefficient.

        """

elif sys.version_info >= (3, 10):
    def correlation(x: Sequence[_Number], y: Sequence[_Number], /) -> float:
        """Pearson's correlation coefficient

        Return the Pearson's correlation coefficient for two inputs. Pearson's
        correlation coefficient *r* takes values between -1 and +1. It measures the
        strength and direction of the linear relationship, where +1 means very
        strong, positive linear relationship, -1 very strong, negative linear
        relationship, and 0 no linear relationship.

        >>> x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        >>> y = [9, 8, 7, 6, 5, 4, 3, 2, 1]
        >>> correlation(x, x)
        1.0
        >>> correlation(x, y)
        -1.0

        """

if sys.version_info >= (3, 10):
    def covariance(x: Sequence[_Number], y: Sequence[_Number], /) -> float:
        """Covariance

        Return the sample covariance of two inputs *x* and *y*. Covariance
        is a measure of the joint variability of two inputs.

        >>> x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        >>> y = [1, 2, 3, 1, 2, 3, 1, 2, 3]
        >>> covariance(x, y)
        0.75
        >>> z = [9, 8, 7, 6, 5, 4, 3, 2, 1]
        >>> covariance(x, z)
        -7.5
        >>> covariance(z, x)
        -7.5

        """

    class LinearRegression(NamedTuple):
        """LinearRegression(slope, intercept)"""

        slope: float
        intercept: float

if sys.version_info >= (3, 11):
    def linear_regression(
        regressor: _SizedIterable[_Number], dependent_variable: _SizedIterable[_Number], /, *, proportional: bool = False
    ) -> LinearRegression:
        """Slope and intercept for simple linear regression.

        Return the slope and intercept of simple linear regression
        parameters estimated using ordinary least squares. Simple linear
        regression describes relationship between an independent variable
        *x* and a dependent variable *y* in terms of a linear function:

            y = slope * x + intercept + noise

        where *slope* and *intercept* are the regression parameters that are
        estimated, and noise represents the variability of the data that was
        not explained by the linear regression (it is equal to the
        difference between predicted and actual values of the dependent
        variable).

        The parameters are returned as a named tuple.

        >>> x = [1, 2, 3, 4, 5]
        >>> noise = NormalDist().samples(5, seed=42)
        >>> y = [3 * x[i] + 2 + noise[i] for i in range(5)]
        >>> linear_regression(x, y)  #doctest: +ELLIPSIS
        LinearRegression(slope=3.17495..., intercept=1.00925...)

        If *proportional* is true, the independent variable *x* and the
        dependent variable *y* are assumed to be directly proportional.
        The data is fit to a line passing through the origin.

        Since the *intercept* will always be 0.0, the underlying linear
        function simplifies to:

            y = slope * x + noise

        >>> y = [3 * x[i] + noise[i] for i in range(5)]
        >>> linear_regression(x, y, proportional=True)  #doctest: +ELLIPSIS
        LinearRegression(slope=2.90475..., intercept=0.0)

        """

elif sys.version_info >= (3, 10):
    def linear_regression(regressor: _SizedIterable[_Number], dependent_variable: _SizedIterable[_Number], /) -> LinearRegression:
        """Slope and intercept for simple linear regression.

        Return the slope and intercept of simple linear regression
        parameters estimated using ordinary least squares. Simple linear
        regression describes relationship between an independent variable
        *x* and a dependent variable *y* in terms of linear function:

            y = slope * x + intercept + noise

        where *slope* and *intercept* are the regression parameters that are
        estimated, and noise represents the variability of the data that was
        not explained by the linear regression (it is equal to the
        difference between predicted and actual values of the dependent
        variable).

        The parameters are returned as a named tuple.

        >>> x = [1, 2, 3, 4, 5]
        >>> noise = NormalDist().samples(5, seed=42)
        >>> y = [3 * x[i] + 2 + noise[i] for i in range(5)]
        >>> linear_regression(x, y)  #doctest: +ELLIPSIS
        LinearRegression(slope=3.09078914170..., intercept=1.75684970486...)

        """

if sys.version_info >= (3, 13):
    _Kernel: TypeAlias = Literal[
        "normal",
        "gauss",
        "logistic",
        "sigmoid",
        "rectangular",
        "uniform",
        "triangular",
        "parabolic",
        "epanechnikov",
        "quartic",
        "biweight",
        "triweight",
        "cosine",
    ]
    def kde(data: Sequence[float], h: float, kernel: _Kernel = "normal", *, cumulative: bool = False) -> Callable[[float], float]:
        """Kernel Density Estimation:  Create a continuous probability density
        function or cumulative distribution function from discrete samples.

        The basic idea is to smooth the data using a kernel function
        to help draw inferences about a population from a sample.

        The degree of smoothing is controlled by the scaling parameter h
        which is called the bandwidth.  Smaller values emphasize local
        features while larger values give smoother results.

        The kernel determines the relative weights of the sample data
        points.  Generally, the choice of kernel shape does not matter
        as much as the more influential bandwidth smoothing parameter.

        Kernels that give some weight to every sample point:

           normal (gauss)
           logistic
           sigmoid

        Kernels that only give weight to sample points within
        the bandwidth:

           rectangular (uniform)
           triangular
           parabolic (epanechnikov)
           quartic (biweight)
           triweight
           cosine

        If *cumulative* is true, will return a cumulative distribution function.

        A StatisticsError will be raised if the data sequence is empty.

        Example
        -------

        Given a sample of six data points, construct a continuous
        function that estimates the underlying probability density:

            >>> sample = [-2.1, -1.3, -0.4, 1.9, 5.1, 6.2]
            >>> f_hat = kde(sample, h=1.5)

        Compute the area under the curve:

            >>> area = sum(f_hat(x) for x in range(-20, 20))
            >>> round(area, 4)
            1.0

        Plot the estimated probability density function at
        evenly spaced points from -6 to 10:

            >>> for x in range(-6, 11):
            ...     density = f_hat(x)
            ...     plot = ' ' * int(density * 400) + 'x'
            ...     print(f'{x:2}: {density:.3f} {plot}')
            ...
            -6: 0.002 x
            -5: 0.009    x
            -4: 0.031             x
            -3: 0.070                             x
            -2: 0.111                                             x
            -1: 0.125                                                   x
             0: 0.110                                            x
             1: 0.086                                   x
             2: 0.068                            x
             3: 0.059                        x
             4: 0.066                           x
             5: 0.082                                 x
             6: 0.082                                 x
             7: 0.058                        x
             8: 0.028            x
             9: 0.009    x
            10: 0.002 x

        Estimate P(4.5 < X <= 7.5), the probability that a new sample value
        will be between 4.5 and 7.5:

            >>> cdf = kde(sample, h=1.5, cumulative=True)
            >>> round(cdf(7.5) - cdf(4.5), 2)
            0.22

        References
        ----------

        Kernel density estimation and its application:
        https://www.itm-conferences.org/articles/itmconf/pdf/2018/08/itmconf_sam2018_00037.pdf

        Kernel functions in common use:
        https://en.wikipedia.org/wiki/Kernel_(statistics)#kernel_functions_in_common_use

        Interactive graphical demonstration and exploration:
        https://demonstrations.wolfram.com/KernelDensityEstimation/

        Kernel estimation of cumulative distribution function of a random variable with bounded support
        https://www.econstor.eu/bitstream/10419/207829/1/10.21307_stattrans-2016-037.pdf

        """

    def kde_random(
        data: Sequence[float], h: float, kernel: _Kernel = "normal", *, seed: _Seed | None = None
    ) -> Callable[[], float]:
        """Return a function that makes a random selection from the estimated
        probability density function created by kde(data, h, kernel).

        Providing a *seed* allows reproducible selections within a single
        thread.  The seed may be an integer, float, str, or bytes.

        A StatisticsError will be raised if the *data* sequence is empty.

        Example:

        >>> data = [-2.1, -1.3, -0.4, 1.9, 5.1, 6.2]
        >>> rand = kde_random(data, h=1.5, seed=8675309)
        >>> new_selections = [rand() for i in range(10)]
        >>> [round(x, 1) for x in new_selections]
        [0.7, 6.2, 1.2, 6.9, 7.0, 1.8, 2.5, -0.5, -1.8, 5.6]

        """
