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MathGroup Archive 1995

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Interactive input? and sorting FindRoot list

  • To: MATHGROUP at christensen.cybernetics.net
  • Subject: [mg637] Interactive input? and sorting FindRoot list
  • From: REECE_D <REECE+_D%A1%Electromagnetic_Sciences at mcimail.com>
  • Date: Mon, 3 Apr 95 11:03 EST

   Two questions:
   
   1)  Is there a way to have a module execute up to a point, ask the user 
for input and then continue?
   
   2)  How does one take a list of roots returned from
   Table[FindRoot[eq, i], {i,x0,x1,di}] and return only the unique roots?  
The problem I am encountering is that FindRoot will return two or more 
versions of the same root so Union sees them as distinct while in reality 
they are approximations to the same root.  I've tried N[] and 
SetPrecision[] with no luck.
   
   I am trying to write a module which will calculate a characteristic 
equation, plot it, prompt the user for approximate distance between roots 
and then return the first n roots.  I could eliminate the plot and prompt 
if I knew of a robust method to calculate the first n roots of the 
characteristic equation.
   
   Any help/ideas on these questions would be greatly appreciated.
   
   Daryl 



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