def verticalfreq(Pot,R):
    """
    
    NAME:
    
       verticalfreq
        
    PURPOSE:
    
        calculate the vertical frequency at R in the potential Pot
    
    INPUT:

       Pot - Potential instance or list thereof
    
       R - Galactocentric radius (can be Quantity)
    
    OUTPUT:
    
        vertical frequency
    
    HISTORY:
    
        2012-07-25 - Written - Bovy (IAS@MPIA)
    
    """
    from .planarPotential import planarPotential
    if isinstance(Pot,(Potential,planarPotential)):
        return Pot.verticalfreq(R,use_physical=False)
    return nu.sqrt(evaluatez2derivs(Pot,R,0.,use_physical=False))
NAME:
    
       verticalfreq
        
    PURPOSE:
    
        calculate the vertical frequency at R in the potential Pot
    
    INPUT:

       Pot - Potential instance or list thereof
    
       R - Galactocentric radius (can be Quantity)
    
    OUTPUT:
    
        vertical frequency
    
    HISTORY:
    
        2012-07-25 - Written - Bovy (IAS@MPIA)