code: def evaluateRforces(Pot,R,z,phi=None,t=0.,v=None):
      
      return _evaluateRforces(Pot,R,z,phi=phi,t=t,v=v)
docs: NAME:
  
         evaluateRforce
  
      PURPOSE:
  
         convenience function to evaluate a possible sum of potentials
  
      INPUT:
  
         Pot - a potential or list of potentials
  
         R - cylindrical Galactocentric distance (can be Quantity)
  
         z - distance above the plane (can be Quantity)
  
         phi - azimuth (optional; can be Quantity))
  
         t - time (optional; can be Quantity)
  
         v - current velocity in cylindrical coordinates (optional, but required when including dissipative forces; can be a Quantity)
  
      OUTPUT:
  
         F_R(R,z,phi,t)
  
      HISTORY:
  
         2010-04-16 - Written - Bovy (NYU)
  
         2018-03-16 - Added velocity input for dissipative forces - Bovy (UofT)