def misalignment(self,isotropic=False,**kwargs):
        """
        NAME:

           misalignment

        PURPOSE:

           calculate the misalignment between the progenitor's frequency
           and the direction along which the stream disrupts

        INPUT:

           isotropic= (False), if True, return the misalignment assuming an isotropic action distribution

        OUTPUT:

           misalignment in rad

        HISTORY:

           2013-12-05 - Written - Bovy (IAS)

           2017-10-28 - Changed output unit to rad - Bovy (UofT)

        """
        warnings.warn("In versions >1.3, the output unit of streamdf.misalignment has been changed to radian (from degree before)",galpyWarning)
        if isotropic:
            dODir= self._dOdJpEig[1][:,numpy.argmax(numpy.fabs(self._dOdJpEig[0]))]
        else:
            dODir= self._dsigomeanProgDirection
        out= numpy.arccos(numpy.sum(self._progenitor_Omega*dODir)/numpy.sqrt(numpy.sum(self._progenitor_Omega**2.)))
        if out > numpy.pi/2.: return out-numpy.pi
        else: return out