Module « scipy.special »

Fonction factorial2 - module scipy.special

Signature de la fonction factorial2

def factorial2(n, exact=False) 

Description

factorial2.__doc__

Double factorial.

    This is the factorial with every second value skipped.  E.g., ``7!! = 7 * 5
    * 3 * 1``.  It can be approximated numerically as::

      n!! = special.gamma(n/2+1)*2**((m+1)/2)/sqrt(pi)  n odd
          = 2**(n/2) * (n/2)!                           n even

    Parameters
    ----------
    n : int or array_like
        Calculate ``n!!``.  Arrays are only supported with `exact` set
        to False.  If ``n < 0``, the return value is 0.
    exact : bool, optional
        The result can be approximated rapidly using the gamma-formula
        above (default).  If `exact` is set to True, calculate the
        answer exactly using integer arithmetic.

    Returns
    -------
    nff : float or int
        Double factorial of `n`, as an int or a float depending on
        `exact`.

    Examples
    --------
    >>> from scipy.special import factorial2
    >>> factorial2(7, exact=False)
    array(105.00000000000001)
    >>> factorial2(7, exact=True)
    105