Plot data for phase diagram.
        2-comp - Full hull with energies
        3/4-comp - Projection into 2D or 3D Gibbs triangle.

        Returns:
            (lines, stable_entries, unstable_entries):
            - lines is a list of list of coordinates for lines in the PD.
            - stable_entries is a {coordinate : entry} for each stable node
            in the phase diagram. (Each coordinate can only have one
            stable phase)
            - unstable_entries is a {entry: coordinates} for all unstable
            nodes in the phase diagram.

def pd_plot_data(self):
        """
        Plot data for phase diagram.
        2-comp - Full hull with energies
        3/4-comp - Projection into 2D or 3D Gibbs triangle.

        Returns:
            (lines, stable_entries, unstable_entries):
            - lines is a list of list of coordinates for lines in the PD.
            - stable_entries is a {coordinate : entry} for each stable node
            in the phase diagram. (Each coordinate can only have one
            stable phase)
            - unstable_entries is a {entry: coordinates} for all unstable
            nodes in the phase diagram.
        """
        pd = self._pd
        entries = pd.qhull_entries
        data = np.array(pd.qhull_data)
        lines = []
        stable_entries = {}
        for line in self.lines:
            entry1 = entries[line[0]]
            entry2 = entries[line[1]]
            if self._dim < 3:
                x = [data[line[0]][0], data[line[1]][0]]
                y = [pd.get_form_energy_per_atom(entry1),
                     pd.get_form_energy_per_atom(entry2)]
                coord = [x, y]
            elif self._dim == 3:
                coord = triangular_coord(data[line, 0:2])
            else:
                coord = tet_coord(data[line, 0:3])
            lines.append(coord)
            labelcoord = list(zip(*coord))
            stable_entries[labelcoord[0]] = entry1
            stable_entries[labelcoord[1]] = entry2

        all_entries = pd.all_entries
        all_data = np.array(pd.all_entries_hulldata)
        unstable_entries = dict()
        stable = pd.stable_entries
        for i in range(0, len(all_entries)):
            entry = all_entries[i]
            if entry not in stable:
                if self._dim < 3:
                    x = [all_data[i][0], all_data[i][0]]
                    y = [pd.get_form_energy_per_atom(entry),
                         pd.get_form_energy_per_atom(entry)]
                    coord = [x, y]
                elif self._dim == 3:
                    coord = triangular_coord([all_data[i, 0:2],
                                              all_data[i, 0:2]])
                else:
                    coord = tet_coord([all_data[i, 0:3], all_data[i, 0:3],
                                       all_data[i, 0:3]])
                labelcoord = list(zip(*coord))
                unstable_entries[entry] = labelcoord[0]

        return lines, stable_entries, unstable_entries