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MathGroup Archive 2005

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Re: problem with FindRoot

  • To: mathgroup at smc.vnet.net
  • Subject: [mg54055] Re: [mg54035] problem with FindRoot
  • From: "Wolf, Hartmut" <Hartmut.Wolf at t-systems.com>
  • Date: Wed, 9 Feb 2005 09:27:28 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

>-----Original Message-----
>From: qfwfq [mailto:qfwfq_0 at yahoo.com] 
To: mathgroup at smc.vnet.net
>Sent: Tuesday, February 08, 2005 11:31 AM
>To: mathgroup at smc.vnet.net
>Subject: [mg54055] [mg54035] problem with FindRoot
>
>Hi all!
>
>I have four equations (eq1=0, ..., eq4=0) with the the four 
>unknowns (y1, y2, y3, y4) in exponentials. I know the interval 
>where the solutions are, and I solve this equation set by 
>means of FindRoot by obtaining set of solutions. Then, I make 
>a selection between the obtained results.
>
>However, I have a dependency between variables: y1<y2<y3<y4
>
>
>mR = Table[FindRoot[{eqn1 == 0, eqn2 == 0, eqn3 == 0, eqn4 == 
>0}, {y1, Random[Real, {a, b}]}, {y2, Random[Real, {a, b}]}, 
>{y3, Random[Real, {a, b}]}, {y4, Random[Real, {a, b}]}], {24}];
>
>My question is
>
>Is there any way of include the relation between y1, ..., y4 
>in the selection of them by Random. Something like {y2, 
>Random[Real, {y1, b}]}, {y3, Random[Real, {y2, b}]}, ...
>
>I hope I have clearly explained my problem.
>
>Thanks
>
>

Would this be what you intended, ordered starting values?

mR = Table[
      With[{{s1, s2, s3, s4} = Sort[Table[Random[Real, {a, b}], {4}]]}, 
        FindRoot[{eqn1 == 0, eqn2 == 0, eqn3 == 0, eqn4 == 0}, {y1, s1},
{y2, 
            s2}, {y3, s3}, {y4, s4}]], {24}];

but this won't garantee anything for your solutions.

--
Hartmut Wolf



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