Module « scipy.special »

Fonction factorial - module scipy.special

Signature de la fonction factorial

def factorial(n, exact=False) 

Description

factorial.__doc__

    The factorial of a number or array of numbers.

    The factorial of non-negative integer `n` is the product of all
    positive integers less than or equal to `n`::

        n! = n * (n - 1) * (n - 2) * ... * 1

    Parameters
    ----------
    n : int or array_like of ints
        Input values.  If ``n < 0``, the return value is 0.
    exact : bool, optional
        If True, calculate the answer exactly using long integer arithmetic.
        If False, result is approximated in floating point rapidly using the
        `gamma` function.
        Default is False.

    Returns
    -------
    nf : float or int or ndarray
        Factorial of `n`, as integer or float depending on `exact`.

    Notes
    -----
    For arrays with ``exact=True``, the factorial is computed only once, for
    the largest input, with each other result computed in the process.
    The output dtype is increased to ``int64`` or ``object`` if necessary.

    With ``exact=False`` the factorial is approximated using the gamma
    function:

    .. math:: n! = \Gamma(n+1)

    Examples
    --------
    >>> from scipy.special import factorial
    >>> arr = np.array([3, 4, 5])
    >>> factorial(arr, exact=False)
    array([   6.,   24.,  120.])
    >>> factorial(arr, exact=True)
    array([  6,  24, 120])
    >>> factorial(5, exact=True)
    120