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Re: My problem when solving a system of equations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg78067] Re: My problem when solving a system of equations
  • From: dh <dh at metrohm.ch>
  • Date: Fri, 22 Jun 2007 06:38:47 -0400 (EDT)
  • References: <f5dkv7$13j$1@smc.vnet.net>


Hi,

in version 5.1 I get overflow messages, but still a result.

in version 6. I get the following output without any message:

{{p->2.29251}}

{{pA->4.44537,p1->2.31915,p2->2.25392,disA->0.996607},{pA->3.97324,p1->4.9583,p2->2.9492,disA->1.73173}}

hope this helps, Daniel



loveinla at gmail.com wrote:

> Hi, guys,

> 

> I was trying to solve a system of nonlinear equations. However,

> whenever I run it, Mathematica always returns:

> " ReplaceAll::reps: {-0.04\(-24 + 5\pA)\((25 - 4\p1)\(-2 + p1) - (24 -

> \

> 5\pA)\(-3 + pA) + (-3 - disA + pA)\(24 - 5\(-disA + pA))) + 0.4\(\

> \[LeftSkeleton]1\[RightSkeleton])\(\[LeftSkeleton]1\[RightSkeleton])

> == 0, \

> \[LeftSkeleton]3\[RightSkeleton]} is neither a list of replacement

> rules nor \

> a valid dispatch table, and so cannot be used for replacing. "

> 

> I don't know what this means and how to deal with it.

> 

> Below is my code for your reference:

> 

> a = 24;

> b = 5;

> c = 25;

> d = 4;

> cA = 3;

> cB = 2;

> t = 5;

> alpha = 0;

> bta = 0.6;

> NB = NSolve[{-d(p - cB) + c - d*p == (p - cB)(c - d*p)^2/t}, {p}];

> SNB = DeleteCases[NB, {p -> _Complex}]

> B = NSolve[{(alpha + (1 - alpha - bta)*(0.5 - ((d/

>           2)*(p1^2 - p2^2) - c*(p1 - p2))/(2t) - ((b/2)*((

>       pA - disA)^2 - pA^2) + a*disA)/(2t)))*(a - b*pA - b*(pA -

>     cA)) - (1 - alpha - bta)*((p1 - cB)*(c - d*

>     p1) + (pA - disA - cA)*(a - b*(pA -

>                    disA)) - (pA - cA)*(a - b*pA))*(-(

>                     a - b*pA)/(

>                         2t)) == 0, (1 - alpha - bta)*((a - b*(pA -

> disA) -

>                                b(pA - disA - cA))*(0.5 + ((d/2)*(

>                         p1^2 - p2^2) - c*(

>                                 p1 - p2))/(2t) + ((b/2)*((pA -

>                                     disA)^2 - pA^2) + a*disA)/(2t)) +

> ((

>                           p1 - cB)*(c -

>               d*p1) + (pA - disA - cA)(a - b*(pA - disA)) - (pA -

>             cA)(a - b*pA))*(-(a - b*(pA - disA))/(

>               2t))) == 0, (1 - alpha)*((c - d*p1 - d*(p1 -

>                   cB))*(0.5 + ((d/2)*(p1^2 - p2^2) - c*(p1 -

>                         p2))/(2t)) + (p1 - cB)*(c - d*p1)*(-

>                   c + d*p1)/(2t)) + (1 -

>                      alpha - bta)*(((pA - disA - cA)*(a -

> 

>                   b*(pA - disA)) - (pA - cA)*(a - b*

>         pA))*(-c + d*p1)/(2t) + (c - d*p1 - d(

>             p1 - cB))*((

>                       b/2)((pA - disA)^2 - pA^2) + a*disA)/(2t)) ==

>                           0, (1 - alpha)*((c - d*p2 - d(p2 - cB))*(

>         0.5 - ((d/

>                   2)*(p1^2 - p2^2) - c*(p1 - p2))/(2t)) + (

>                         p2 - cB)*(c - d*p2)*(-c + d*p2)/(

>                         2t)) - (1 - alpha - bta)*(c - d*p2 - d(p2 -

> cB))*((

>                               b/2)*((pA - disA)^2 - pA^2) + a*disA)/(

>                   2t) == 0}, {pA, p1, p2, disA}];

> BR = DeleteCases[B, {pA -> _Complex, p1 -> _Complex,

>              p2 -> _Complex, disA -> _Complex}];

> SB = Select[BR, And @@ (({pA > 0, p1 > 0, p2 >

>                0, disA > 0, pA - disA > 0} /. #)) &]

> 

> 




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