dtype=np.float64)
    0.55000000074505806 # may vary

    Specifying a where argument:

    >>> a = np.array([[5, 9, 13], [14, 10, 12], [11, 15, 19]])
    >>> np.mean(a)
    12.0
    >>> np.mean(a, where=[[True], [False], [False]])
    9.0

    rą