def plot_intrusion_curve(self, fig=None):
        r"""
        Plot the percolation curve as the invader volume or number fraction vs
        the applied capillary pressure.

        """
        # Begin creating nicely formatted plot
        x, y = self.get_intrusion_data()
        if fig is None:
            fig = plt.figure()
        plt.semilogx(x, y, 'ko-')
        plt.ylabel('Invading Phase Saturation')
        plt.xlabel('Capillary Pressure')
        plt.grid(True)
        return fig
r"""
        Plot the percolation curve as the invader volume or number fraction vs
        the applied capillary pressure.