def _dens(self,R,z,phi=0.,t=0.):
        """
        NAME:
           _dens
        PURPOSE:
           evaluate the density for this potential
        INPUT:
           R - Galactocentric cylindrical radius
           z - vertical height
           phi - azimuth
           t - time
        OUTPUT:
           the density
        HISTORY:
           2016-11-04 - Written - Bovy (UofT/CCA)
        """
        x,y,z= self._compute_xyz(R,phi,z,t)
        zc= numpy.sqrt(z**2.+self._c2)
        bzc2= (self._b+zc)**2.
        bigA= self._b*y**2.+(self._b+3.*zc)*bzc2
        bigC= y**2.+bzc2
        return self._c2/24./numpy.pi/self._a/bigC**2./zc**3.\
            *((x+self._a)*(3.*bigA*bigC+(2.*bigA+self._b*bigC)*(x+self._a)**2.)\
                  /(bigC+(x+self._a)**2.)**1.5\
             -(x-self._a)*(3.*bigA*bigC+(2.*bigA+self._b*bigC)*(x-self._a)**2.)\
                  /(bigC+(x-self._a)**2.)**1.5)
def _dens ( self , R , z , phi = 0. , t = 0. ) : x , y , z = self . _compute_xyz ( R , phi , z , t ) zc = numpy . sqrt ( z ** 2. + self . _c2 ) bzc2 = ( self . _b + zc ) ** 2. bigA = self . _b * y ** 2. + ( self . _b + 3. * zc ) * bzc2 bigC = y ** 2. + bzc2 return self . _c2 / 24. / numpy . pi / self . _a / bigC ** 2. / zc ** 3. * ( ( x + self . _a ) * ( 3. * bigA * bigC + ( 2. * bigA + self . _b * bigC ) * ( x + self . _a ) ** 2. ) / ( bigC + ( x + self . _a ) ** 2. ) ** 1.5 - ( x - self . _a ) * ( 3. * bigA * bigC + ( 2. * bigA + self . _b * bigC ) * ( x - self . _a ) ** 2. ) / ( bigC + ( x - self . _a ) ** 2. ) ** 1.5 )
NAME:
           _dens
        PURPOSE:
           evaluate the density for this potential
        INPUT:
           R - Galactocentric cylindrical radius
           z - vertical height
           phi - azimuth
           t - time
        OUTPUT:
           the density
        HISTORY:
           2016-11-04 - Written - Bovy (UofT/CCA)