def sampleVRVT(self,R,n=1,nsigma=None,target=True):
        """
        NAME:

           sampleVRVT

        PURPOSE:

           sample a radial and azimuthal velocity at R

        INPUT:

           R - Galactocentric distance (can be Quantity)

           n= number of distances to sample

           nsigma= number of sigma to rejection-sample on

           target= if True, sample using the 'target' sigma_R rather than the actual sigma_R (default=True)

        OUTPUT:

           list of samples

        BUGS:

           should use the fact that vR and vT separate

        HISTORY:

           2011-03-24 - Written - Bovy (NYU)

        """
        #Determine where the max of the v-distribution is using asymmetric drift
        maxVR= 0.
        maxVT= optimize.brentq(_vtmaxEq,0.,R**self._beta+0.2,(R,self))
        maxVD= self(Orbit([R,maxVR,maxVT]))
        #Now rejection-sample
        if nsigma == None:
            nsigma= _NSIGMA
        out= []
        if target:
            sigma= math.sqrt(self.targetSigma2(R,use_physical=False))
        else:
            sigma= math.sqrt(self.sigma2(R,use_physical=False))
        while len(out) < n:
            #sample
            vrg, vtg= nu.random.normal(), nu.random.normal()
            propvR= vrg*nsigma*sigma
            propvT= vtg*nsigma*sigma/self._gamma+maxVT
            VDatprop= self(Orbit([R,propvR,propvT]))
            if VDatprop/maxVD > nu.random.uniform()*nu.exp(-0.5*(vrg**2.+vtg**2.)): #accept
                out.append(sc.array([propvR,propvT]))
        return nu.array(out)
NAME:

           sampleVRVT

        PURPOSE:

           sample a radial and azimuthal velocity at R

        INPUT:

           R - Galactocentric distance (can be Quantity)

           n= number of distances to sample

           nsigma= number of sigma to rejection-sample on

           target= if True, sample using the 'target' sigma_R rather than the actual sigma_R (default=True)

        OUTPUT:

           list of samples

        BUGS:

           should use the fact that vR and vT separate

        HISTORY:

           2011-03-24 - Written - Bovy (NYU)