Example 2.  Fit the curve  [Graphics:Images/NonLinearCurveFitMod_gr_87.gif]  to the data points  [Graphics:Images/NonLinearCurveFitMod_gr_88.gif].  

Solution 2.

Enter the point into a two dimensional array xys which stores points in the xy-plane.  

[Graphics:../Images/NonLinearCurveFitMod_gr_89.gif]

[Graphics:../Images/NonLinearCurveFitMod_gr_90.gif]

Look at the transpose of this "list of lists."

[Graphics:../Images/NonLinearCurveFitMod_gr_91.gif]

[Graphics:../Images/NonLinearCurveFitMod_gr_92.gif]

The two portions of this data structure are separated by  breaking off the first and second parts of the "list of lists"  [Graphics:../Images/NonLinearCurveFitMod_gr_93.gif]  and  [Graphics:../Images/NonLinearCurveFitMod_gr_94.gif].  

[Graphics:../Images/NonLinearCurveFitMod_gr_95.gif]

[Graphics:../Images/NonLinearCurveFitMod_gr_96.gif]
[Graphics:../Images/NonLinearCurveFitMod_gr_97.gif]

We want to use the logarithm of the abscissas and the logarithm of the ordinates.

[Graphics:../Images/NonLinearCurveFitMod_gr_98.gif]

[Graphics:../Images/NonLinearCurveFitMod_gr_99.gif]
[Graphics:../Images/NonLinearCurveFitMod_gr_100.gif]

[Graphics:../Images/NonLinearCurveFitMod_gr_101.gif]
[Graphics:../Images/NonLinearCurveFitMod_gr_102.gif]

[Graphics:../Images/NonLinearCurveFitMod_gr_103.gif]
[Graphics:../Images/NonLinearCurveFitMod_gr_104.gif]

Now "glue together" the transformed parts to form the pairs  [Graphics:../Images/NonLinearCurveFitMod_gr_105.gif]  and store them in the two dimensional array XYs which stores points in the XY-plane.  

[Graphics:../Images/NonLinearCurveFitMod_gr_106.gif]

[Graphics:../Images/NonLinearCurveFitMod_gr_107.gif]

Now use the Mathematica procedure  Fit  to get the least squares line in the XY-plane.  Then we shall graph this line in the transformed XY-plane.

[Graphics:../Images/NonLinearCurveFitMod_gr_108.gif]


[Graphics:../Images/NonLinearCurveFitMod_gr_109.gif]
[Graphics:../Images/NonLinearCurveFitMod_gr_110.gif]
[Graphics:../Images/NonLinearCurveFitMod_gr_111.gif]

Now plot the "least squares line"  [Graphics:../Images/NonLinearCurveFitMod_gr_112.gif]  in the XY-plane.

[Graphics:../Images/NonLinearCurveFitMod_gr_113.gif]


[Graphics:../Images/NonLinearCurveFitMod_gr_114.gif]

[Graphics:../Images/NonLinearCurveFitMod_gr_115.gif]
[Graphics:../Images/NonLinearCurveFitMod_gr_116.gif]

To get back to xy space we could copy the coefficients from  g  or we could go looking inside Mathematica to see where they are kept. The data structure of  g  looks like:

[Graphics:../Images/NonLinearCurveFitMod_gr_117.gif]
[Graphics:../Images/NonLinearCurveFitMod_gr_118.gif]

So the coefficients  A  is located at [Graphics:../Images/NonLinearCurveFitMod_gr_119.gif] and  B  is located at [Graphics:../Images/NonLinearCurveFitMod_gr_120.gif].  

[Graphics:../Images/NonLinearCurveFitMod_gr_121.gif]

[Graphics:../Images/NonLinearCurveFitMod_gr_122.gif]
[Graphics:../Images/NonLinearCurveFitMod_gr_123.gif]

Now we are in business, we use  [Graphics:../Images/NonLinearCurveFitMod_gr_124.gif]  and a = A to get the coefficients of  [Graphics:../Images/NonLinearCurveFitMod_gr_125.gif]  back in the original  xy-plane.

[Graphics:../Images/NonLinearCurveFitMod_gr_126.gif]

[Graphics:../Images/NonLinearCurveFitMod_gr_127.gif]
[Graphics:../Images/NonLinearCurveFitMod_gr_128.gif]
[Graphics:../Images/NonLinearCurveFitMod_gr_129.gif]
[Graphics:../Images/NonLinearCurveFitMod_gr_130.gif]
[Graphics:../Images/NonLinearCurveFitMod_gr_131.gif]
[Graphics:../Images/NonLinearCurveFitMod_gr_132.gif]

Now graph the function  [Graphics:../Images/NonLinearCurveFitMod_gr_133.gif]  in the xy-plane.

[Graphics:../Images/NonLinearCurveFitMod_gr_134.gif]


[Graphics:../Images/NonLinearCurveFitMod_gr_135.gif]

[Graphics:../Images/NonLinearCurveFitMod_gr_136.gif]

[Graphics:../Images/NonLinearCurveFitMod_gr_137.gif]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(c) John H. Mathews 2004