figure 1. This curve then, is to be emulated using the Matchacurve process detailed in 

 the steps below: 



1. Let Xp be the value of X at or near the largest X-value in the data set. Let 

 Yr, be the val ue of Y at Xp, Determine the values of Xp (-800) and Yp (=66) as shown in 

 figure 1. Note that for sets 1 and 2, Yp is measured at X = or at Xp depending on 

 position--see table 1. Select representative point coordinates from the smoothed curve. 



Five points have been chosen for this example.— Call the array of X values X. , and 

 the array of Y values, Y^. 



Point coordinates from the smoothed curve. 



X. 

 1 







200 



400 



600 



800 



Y. 

 1 







1.3 



10.6 



31.4 



66 



2. Scale the X. to X . /X and the Y. to Y./Y . 



1 1 p 1 1 p 



Scaled coordinates 



X./800 

 1 



0.00 



0.25 



0.50 



0.75 



1.00 



Y^/66 



0.00 



0.02 



0. 16 



0.48 



1.00 



3. Plot these points on a sheet of graph paper at the exact scale- shown in 

 figure 2. Draw a smooth curve through the points. 



4. From table 1, identify the "position"--position A, here--of the scaled curve 

 in figure 2. Then use the scaled curve as an overlay for Set 1 and Set 2 of the 

 Standards, position A; be certain that the X and Y axes are matched exactly. Find the 

 Standards that bracket the overlay curve of figure 3.—^ In this case, n = 2.5 and 3.0 of 

 Set 1 bracket the overlay curve nicely. Use proportional departure of the overlay curve 

 from the left bracketing Standard to approximate an interpolated value between n = 2.5 

 and 3.0. This is best done at a point where curve form accuracy is most crucial--the 

 point of sharpest bend was adopted in this case. From figure 3 the interpolated n is 

 2.7. 



-^se fewer points where the desired sensitivity is less, more for greater 

 sensitivity. 



^his is the same scale used for the Standards. Note that the odd X scale was 

 necessitated by publication limitations on paper size. 



—'a light source behind the graphs that are being compared will assist in the 

 matching process . 



3 



