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