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Module « scipy.special »

Fonction j1 - module scipy.special

Signature de la fonction j1

def j1(*args, **kwargs) 

Description

help(scipy.special.j1)

j1(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True[, signature])


    j1(x, out=None)

    Bessel function of the first kind of order 1.

    Parameters
    ----------
    x : array_like
        Argument (float).
    out : ndarray, optional
        Optional output array for the function values

    Returns
    -------
    J : scalar or ndarray
        Value of the Bessel function of the first kind of order 1 at `x`.

    See Also
    --------
    jv: Bessel function of the first kind
    spherical_jn: spherical Bessel functions.

    Notes
    -----
    The domain is divided into the intervals [0, 8] and (8, infinity). In the
    first interval a 24 term Chebyshev expansion is used. In the second, the
    asymptotic trigonometric representation is employed using two rational
    functions of degree 5/5.

    This function is a wrapper for the Cephes [1]_ routine `j1`.
    It should not be confused with the spherical Bessel functions (see
    `spherical_jn`).

    References
    ----------
    .. [1] Cephes Mathematical Functions Library,
           http://www.netlib.org/cephes/

    Examples
    --------
    Calculate the function at one point:

    >>> from scipy.special import j1
    >>> j1(1.)
    0.44005058574493355

    Calculate the function at several points:

    >>> import numpy as np
    >>> j1(np.array([-2., 0., 4.]))
    array([-0.57672481,  0.        , -0.06604333])

    Plot the function from -20 to 20.

    >>> import matplotlib.pyplot as plt
    >>> fig, ax = plt.subplots()
    >>> x = np.linspace(-20., 20., 1000)
    >>> y = j1(x)
    >>> ax.plot(x, y)
    >>> plt.show()
    

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