Plot the equation of state.

        Args:
            width (float): Width of plot in inches. Defaults to 8in.
            height (float): Height of plot in inches. Defaults to width *
                golden ratio.
            plt (matplotlib.pyplot): If plt is supplied, changes will be made
                to an existing plot. Otherwise, a new plot will be created.
            dpi:
            kwargs (dict): additional args fed to pyplot.plot.
                supported keys: style, color, text, label

        Returns:
            Matplotlib plot object.

def plot(self, width=8, height=None, plt=None, dpi=None, **kwargs):
        """
        Plot the equation of state.

        Args:
            width (float): Width of plot in inches. Defaults to 8in.
            height (float): Height of plot in inches. Defaults to width *
                golden ratio.
            plt (matplotlib.pyplot): If plt is supplied, changes will be made
                to an existing plot. Otherwise, a new plot will be created.
            dpi:
            kwargs (dict): additional args fed to pyplot.plot.
                supported keys: style, color, text, label

        Returns:
            Matplotlib plot object.
        """
        plt = pretty_plot(width=width, height=height, plt=plt, dpi=dpi)

        color = kwargs.get("color", "r")
        label = kwargs.get("label", "{} fit".format(self.__class__.__name__))
        lines = ["Equation of State: %s" % self.__class__.__name__,
                 "Minimum energy = %1.2f eV" % self.e0,
                 "Minimum or reference volume = %1.2f Ang^3" % self.v0,
                 "Bulk modulus = %1.2f eV/Ang^3 = %1.2f GPa" %
                 (self.b0, self.b0_GPa),
                 "Derivative of bulk modulus wrt pressure = %1.2f" % self.b1]
        text = "\n".join(lines)
        text = kwargs.get("text", text)

        # Plot input data.
        plt.plot(self.volumes, self.energies, linestyle="None", marker="o",
                 color=color)

        # Plot eos fit.
        vmin, vmax = min(self.volumes), max(self.volumes)
        vmin, vmax = (vmin - 0.01 * abs(vmin), vmax + 0.01 * abs(vmax))
        vfit = np.linspace(vmin, vmax, 100)

        plt.plot(vfit, self.func(vfit), linestyle="dashed", color=color,
                 label=label)

        plt.grid(True)
        plt.xlabel("Volume $\\AA^3$")
        plt.ylabel("Energy (eV)")
        plt.legend(loc="best", shadow=True)
        # Add text with fit parameters.
        plt.text(0.4, 0.5, text, transform=plt.gca().transAxes)

        return plt