; Given type (string, e.g, "O"), subtype (float, e.g. 3)
; and class (integer), return V-R from
; AQ 4th ed
;

function aq_vr, type, subtype, class
  functionname = 'aq_vr'
  CASE class OF
    5: begin ; Main sequence
	    CASE type OF
		'O': begin 
			x = [5,9] & y = [-0.15, -0.15]
		     end
		'B': begin 
			x = [0,2,5,8] & y = [-0.13, -0.10, -0.06, -0.02]
		     end
		'A': begin 
			x = [0,2,5] & y = [0.02, 0.08, 0.16]
		     end
		'F': begin 
			x = [0,2,5,8] & y = [0.30, 0.35, 0.40, 0.47]
		     end
		'G': begin 
			x = [0,2,5,8] & y = [0.50, 0.53, 0.54, 0.58]
		     end
		'K': begin 
			x = [0,2,5] & y = [0.64, 0.74, 0.99]
		     end
		'M': begin 
			x = [0,2,5] & y = [1.28, 1.50, 1.80]
		     end
	  ENDCASE
       end
    3: begin ; giants. Teff for O-F are from xx
	    CASE type OF
		'G': begin 
			x = [5,8] & y = [0.69, 0.70]
		     end
		'K': begin 
			x = [0,2,5] & y = [0.77, 0.84, 1.20]
		     end
		'M': begin 
			x = [0,2,5] & y = [1.23, 1.34, 2.18]
		     end
		 ELSE: begin ; out of bounds! 
		    print, functionname+': spectral type out of bounds'
		    return, -100
		    end
	  ENDCASE
       end
    1: begin ; super giants. 
	    CASE type OF
		'B': begin 
 			   x = [2,5,8] 
			   y = [-0.05, 0.02, 0.02]
		     end
		'A': begin 
			x = [0,2,5] & y = [0.03, 0.07, 0.12]
		     end
		'F': begin 
			x = [0,2,5,8] & y = [0.21, 0.26, 0.35, 0.45]
		     end
		'G': begin 
			x = [0,2,5,8] & y = [0.51, 0.58, 0.67, 0.69]
		     end
		'K': begin 
			x = [0,2,5] & y = [0.76, 0.85, 1.20]
		     end
		'M': begin 
			x = [0,2,5] & y = [1.23, 1.34, 2.18]
		     end
		  ELSE: begin ; out of bounds! 
		    print, functionname+': spectral type out of bounds'
		    return, -100
		    end
	  ENDCASE
       end
  ELSE: begin ; out of bounds! 
    print, functionname+': spectral type out of bounds'
    return, -100
    end
  ENDCASE

  res = poly_fit(x, y, 1) 
  color = poly(subtype,res)
  return, color
end