          ax.loglog(range(1, 360, 5), range(1, 360, 5))
            ax.set_xlabel('frequency [Hz]')

            def invert(x):
                # 1/x with special treatment of x == 0
                x = np.array(x).astype(float)
                near_zero = np.isclose(x, 0)
                x[near_zero] = np.inf
                x[~near_zero] = 1 / x[~near_zero]
                return x

            # the inverse of 1/x is itself
            secax = ax.secondary_xaxis('top', functions=(invert, invert))
            secax.set_xlabel('Period [s]')
            plt.show()
        )