def plotProgenitor(self,d1='x',d2='z',*args,**kwargs):
        """
        NAME:

           plotProgenitor

        PURPOSE:

           plot the progenitor orbit

        INPUT:

           d1= plot this on the X axis ('x','y','z','R','phi','vx','vy','vz','vR','vt','ll','bb','dist','pmll','pmbb','vlos')

           d2= plot this on the Y axis (same list as for d1)

           scaleToPhysical= (False), if True, plot positions in kpc and velocities in km/s

           bovy_plot.bovy_plot args and kwargs

        OUTPUT:

           plot to output device

        HISTORY:

           2013-12-09 - Written - Bovy (IAS)

        """
        tts= self._progenitor._orb.t[self._progenitor._orb.t \
                                          < self._trackts[self._nTrackChunks-1]]
        obs= [self._R0,0.,self._Zsun]
        obs.extend(self._vsun)
        phys= kwargs.pop('scaleToPhysical',False)
        tx= self._parse_progenitor_dim(d1,tts,ro=self._ro,vo=self._vo,
                                       obs=obs,phys=phys)
        ty= self._parse_progenitor_dim(d2,tts,ro=self._ro,vo=self._vo,
                                       obs=obs,phys=phys)
        bovy_plot.bovy_plot(tx,ty,*args,
                            xlabel=_labelDict[d1.lower()],
                            ylabel=_labelDict[d2.lower()],
                            **kwargs)
        return None
NAME:

           plotProgenitor

        PURPOSE:

           plot the progenitor orbit

        INPUT:

           d1= plot this on the X axis ('x','y','z','R','phi','vx','vy','vz','vR','vt','ll','bb','dist','pmll','pmbb','vlos')

           d2= plot this on the Y axis (same list as for d1)

           scaleToPhysical= (False), if True, plot positions in kpc and velocities in km/s

           bovy_plot.bovy_plot args and kwargs

        OUTPUT:

           plot to output device

        HISTORY:

           2013-12-09 - Written - Bovy (IAS)