Example 4.  Determine how much the solutions in example 2 and 3 differ.

Solution 4.

We cannot merely form the difference between the solutions, because they do not have the same dimension.  

[Graphics:../Images/FiniteDifferenceMod_gr_96.gif]
[Graphics:../Images/FiniteDifferenceMod_gr_97.gif]
[Graphics:../Images/FiniteDifferenceMod_gr_98.gif]

We will need to extract every other point from points2 and make a list which contains the same length as points1.

 

[Graphics:../Images/FiniteDifferenceMod_gr_99.gif]

[Graphics:../Images/FiniteDifferenceMod_gr_100.gif]

[Graphics:../Images/FiniteDifferenceMod_gr_101.gif]


[Graphics:../Images/FiniteDifferenceMod_gr_102.gif]

[Graphics:../Images/FiniteDifferenceMod_gr_103.gif]


[Graphics:../Images/FiniteDifferenceMod_gr_104.gif]

[Graphics:../Images/FiniteDifferenceMod_gr_105.gif]


[Graphics:../Images/FiniteDifferenceMod_gr_106.gif]

[Graphics:../Images/FiniteDifferenceMod_gr_107.gif]


[Graphics:../Images/FiniteDifferenceMod_gr_108.gif]

[Graphics:../Images/FiniteDifferenceMod_gr_109.gif]


[Graphics:../Images/FiniteDifferenceMod_gr_110.gif]

[Graphics:../Images/FiniteDifferenceMod_gr_111.gif]

 

 

    Does the error look small? Large? Can it be improved?

    We now use Richardson's improvement scheme and extrapolate the seemingly inaccurate solutions in examples 2 and 3.

We should discover the joy of understanding the order of a numerical method.  

 

 

 

 

 

 

 

 

 

 

 

 

(c) John H. Mathews 2003