@cache_readonly
    def arfreq(self):
        r"""
        Returns the frequency of the AR roots.

        This is the solution, x, to z = abs(z)*exp(2j*np.pi*x) where z are the
        roots.
        """
        z = self.arroots
        if not z.size:
            return
        return np.arctan2(z.imag, z.real) / (2*pi)
dataset/ETHPy150Open statsmodels/statsmodels/statsmodels/tsa/arima_model.py/ARMAResults.arfreq/original