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Module « scipy.special »

Fonction kv - module scipy.special

Signature de la fonction kv

def kv(*args, **kwargs) 

Description

help(scipy.special.kv)

kv(x1, x2, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True[, signature])


    kv(v, z, out=None)

    Modified Bessel function of the second kind of real order `v`

    Returns the modified Bessel function of the second kind for real order
    `v` at complex `z`.

    These are also sometimes called functions of the third kind, Basset
    functions, or Macdonald functions.  They are defined as those solutions
    of the modified Bessel equation for which,

    .. math::
        K_v(x) \sim \sqrt{\pi/(2x)} \exp(-x)

    as :math:`x \to \infty` [3]_.

    Parameters
    ----------
    v : array_like of float
        Order of Bessel functions
    z : array_like of complex
        Argument at which to evaluate the Bessel functions
    out : ndarray, optional
        Optional output array for the function results

    Returns
    -------
    scalar or ndarray
        The results. Note that input must be of complex type to get complex
        output, e.g. ``kv(3, -2+0j)`` instead of ``kv(3, -2)``.

    See Also
    --------
    kve : This function with leading exponential behavior stripped off.
    kvp : Derivative of this function

    Notes
    -----
    Wrapper for AMOS [1]_ routine `zbesk`.  For a discussion of the
    algorithm used, see [2]_ and the references therein.

    References
    ----------
    .. [1] Donald E. Amos, "AMOS, A Portable Package for Bessel Functions
           of a Complex Argument and Nonnegative Order",
           http://netlib.org/amos/
    .. [2] Donald E. Amos, "Algorithm 644: A portable package for Bessel
           functions of a complex argument and nonnegative order", ACM
           TOMS Vol. 12 Issue 3, Sept. 1986, p. 265
    .. [3] NIST Digital Library of Mathematical Functions,
           Eq. 10.25.E3. https://dlmf.nist.gov/10.25.E3

    Examples
    --------
    Plot the function of several orders for real input:

    >>> import numpy as np
    >>> from scipy.special import kv
    >>> import matplotlib.pyplot as plt
    >>> x = np.linspace(0, 5, 1000)
    >>> for N in np.linspace(0, 6, 5):
    ...     plt.plot(x, kv(N, x), label='$K_{{{}}}(x)$'.format(N))
    >>> plt.ylim(0, 10)
    >>> plt.legend()
    >>> plt.title(r'Modified Bessel function of the second kind $K_\nu(x)$')
    >>> plt.show()

    Calculate for a single value at multiple orders:

    >>> kv([4, 4.5, 5], 1+2j)
    array([ 0.1992+2.3892j,  2.3493+3.6j   ,  7.2827+3.8104j])

    

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