def _v_sum(t_arr, i):
    """
    Generates the coefficient V for barycentric coordinates

    Parameters
    ----------
    t_arr : iterable of floats
        values of t
    i : int
        index of current point.

    Returns
    -------
    v_i : float
        coefficient V.

    """
    n = len(t_arr)
    prod_coef = [ii for ii in range(n)]
    prod_coef.pop(i)
    v_i = 1.0
    for jj in prod_coef:
        v_i *= t_arr[i] - t_arr[jj]
    return 1.0 / v_i