def plotEzJz(self,*args,**kwargs):
        """
        NAME:
           plotEzJz
        PURPOSE:
           plot E_z(.)/sqrt(dens(R)) along the orbit
        INPUT:
           pot= Potential instance or list of instances in which the orbit was
                 integrated
           d1= - plot Ez vs d1: e.g., 't', 'z', 'R', 'vR', 'vT', 'vz'      
           +bovy_plot.bovy_plot inputs
        OUTPUT:
           figure to output device
        HISTORY:
           2010-08-08 - Written - Bovy (NYU)
        """
        labeldict= {'t':r'$t$','R':r'$R$','vR':r'$v_R$','vT':r'$v_T$',
                    'z':r'$z$','vz':r'$v_z$','phi':r'$\phi$',
                    'x':r'$x$','y':r'$y$','vx':r'$v_x$','vy':r'$v_y$'}
        if not 'pot' in kwargs:
            try:
                pot= self._pot
            except AttributeError:
                raise AttributeError("Integrate orbit first or specify pot=")
        else:
            pot= kwargs.pop('pot')
        d1= kwargs.pop('d1','t')
        self.EzJz= [(evaluatePotentials(pot,self.orbit[ii,0],self.orbit[ii,3],
                                        t=self.t[ii],use_physical=False)-
                     evaluatePotentials(pot,self.orbit[ii,0],0.,
                                        phi= self.orbit[ii,5],t=self.t[ii],
                                        use_physical=False)+
                     self.orbit[ii,4]**2./2.)/\
                        nu.sqrt(evaluateDensities(pot,self.orbit[ii,0],0.,
                                                  phi=self.orbit[ii,5],
                                                  t=self.t[ii],
                                                  use_physical=False))\
                        for ii in range(len(self.t))]
        if not 'xlabel' in kwargs:
            kwargs['xlabel']= labeldict[d1]
        if not 'ylabel' in kwargs:
            kwargs['ylabel']= r'$E_z/\sqrt{\rho}$'
        if d1 == 't':
            return plot.bovy_plot(nu.array(self.t),
                                  nu.array(self.EzJz)/self.EzJz[0],
                                  *args,**kwargs)
        elif d1 == 'z':
            return plot.bovy_plot(self.orbit[:,3],
                                  nu.array(self.EzJz)/self.EzJz[0],
                                  *args,**kwargs)
        elif d1 == 'R':
            return plot.bovy_plot(self.orbit[:,0],
                                  nu.array(self.EzJz)/self.EzJz[0],
                                  *args,**kwargs)
        elif d1 == 'vR':
            return plot.bovy_plot(self.orbit[:,1],
                                  nu.array(self.EzJz)/self.EzJz[0],
                                  *args,**kwargs)
        elif d1 == 'vT':
            return plot.bovy_plot(self.orbit[:,2],
                                  nu.array(self.EzJz)/self.EzJz[0],
                                  *args,**kwargs)
        elif d1 == 'vz':
            return plot.bovy_plot(self.orbit[:,4],
                                  nu.array(self.EzJz)/self.EzJz[0],
                                  *args,**kwargs)
NAME:
           plotEzJz
        PURPOSE:
           plot E_z(.)/sqrt(dens(R)) along the orbit
        INPUT:
           pot= Potential instance or list of instances in which the orbit was
                 integrated
           d1= - plot Ez vs d1: e.g., 't', 'z', 'R', 'vR', 'vT', 'vz'      
           +bovy_plot.bovy_plot inputs
        OUTPUT:
           figure to output device
        HISTORY:
           2010-08-08 - Written - Bovy (NYU)