def calc_y(f, t):
    """Calc y coordinate by params.

    :param f: the interp params
    :type f: dict
    :param t: the accumulation of steps
    :type t: int
    :return: y coordinate
    :rtype: float
    """
    return f['a_y'] + f['b_y'] * t + f['c_y'] * t * t + f['d_y'] * t * t * t