ray
        The arithmetic-geometric mean of `a` and `b`.

    Examples
    --------
    >>> import numpy as np
    >>> from scipy.special import agm
    >>> a, b = 24.0, 6.0
    >>> agm(a, b)
    13.458171481725614

    Compare that result to the iteration:

    >>> while a != b:
    ...     a, b = (a + b)/2, np.sqrt(a*b)
    ...     print("a = %19.16f  b=%19.16f" % (a, b))
    ...
    a = 15.0000000000000000  b=12.0000000000000000
    a = 13.5000000000000000  b=13.4164078649987388
    a = 13.4582039324993694  b=13.4581390309909850
    a = 13.4581714817451772  b=13.4581714817060547
    a = 13.4581714817256159  b=13.4581714817256159

    When array-like arguments are given, broadcasting applies:

    >>> a = np.array([[1.5], [3], [6]])  # a has shape (3, 1).
    >>> b = np.array([6, 12, 24, 48])    # b has shape (4,).
    >>> agm(a, b)
    array([[  3.36454287,   5.42363427,   9.05798751,  15.53650756],
           [  4.37037309,   6.72908574,  10.84726853,  18.11597502],
           [  6.        ,   8.74074619,  13.45817148,  21.69453707]])
    Ú