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} /. #)) &]
>
>