code: def integrate_dxdv(self,dxdv,t,pot,method='dopr54_c',
                         rectIn=False,rectOut=False):
          
          if hasattr(self,'_orbInterp'): delattr(self,'_orbInterp')
          if hasattr(self,'rs'): delattr(self,'rs')
          thispot= toPlanarPotential(pot)
          self.t= nu.array(t)
          self._pot_dxdv= thispot
          self._pot= thispot
          self.orbit_dxdv, msg= _integrateOrbit_dxdv(self.vxvv,dxdv,thispot,t,
                                                     method,rectIn,rectOut)
          self.orbit= self.orbit_dxdv[:,:4]
          return msg
docs: NAME:
             integrate_dxdv
          PURPOSE:
             integrate the orbit and a small area of phase space
          INPUT:
             dxdv - [dR,dvR,dvT,dphi]
             t - list of times at which to output (0 has to be in this!)
             pot - potential instance or list of instances
             method= 'odeint' for scipy's odeint
                     'rk4_c' for a 4th-order Runge-Kutta integrator in C
                     'rk6_c' for a 6-th order Runge-Kutta integrator in C
                     'dopr54_c' for a Dormand-Prince integrator in C (generally the fastest)
             rectIn= (False) if True, input dxdv is in rectangular coordinates
             rectOut= (False) if True, output dxdv (that in orbit_dxdv) is in rectangular coordinates
          OUTPUT:
             (none) (get the actual orbit using getOrbit_dxdv()
          HISTORY:
             2010-10-17 - Written - Bovy (IAS)
             2014-06-29 - Added rectIn and rectOut - Bovy (IAS)