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MathGroup Archive 2000

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using FindRoot with a list of starting values

  • To: mathgroup at smc.vnet.net
  • Subject: [mg25757] using FindRoot with a list of starting values
  • From: "Lu, Shihua" <SLu at crai.com>
  • Date: Sat, 21 Oct 2000 14:43:10 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Here is the problem.  I need to solve a simultaneous equation system using
FindRoot.  For example, there are 3 equations and 3 unknowns,

FindRoot[{eq1, eq2, eq3},{x,x0},{y,y0},{z,z0}]

However, when I have many unknowns, it is awkward to type in all the
starting values by hand.  Also, if I need to change the starting values in
the middle of the program, or even change the number of unknowns to solve
for, I need to find out a more elegant way to provide inputs to FindRoot.

I tried the following.  First, I built a list,

start={{x,x0},{y,y0},{z,z0}}.

Then, I use the command

FindRoot[{eq1,eq2,eq3},start].

It did not work because start is a Table.

Can someone teach me a trick to make it work?

Many thanks,
Shihua Lu 



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