Re: DSolve for a system of 3 equations
- To: mathgroup at smc.vnet.net
- Subject: [mg36299] Re: DSolve for a system of 3 equations
- From: guillerm at aida.usal.es (Guillermo Sanchez)
- Date: Fri, 30 Aug 2002 01:19:26 -0400 (EDT)
- References: <akkctj$81o$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Neil, They are not a general analitical solution for a system of ODE with 3 or more variables where all coffs. are parameters. I have a package for solving SODE. Perhaps you can find it useful. http://www.mathsource.com/Content/WhatsNew/0211-554 Guillermo Sanchez Neil Klepeis <nklepeis at uclink4.berkeley.edu> wrote in message news:<akkctj$81o$1 at smc.vnet.net>... > I try to solve a three equation linear ODE system with constant > coefficients and Mathematica 3.0 (Intel/Linux) chokes (see below). > > When I try the same thing on Mathematica 4.0 (Solaris) I get a very > strange result containing things like "E^x#1" OR "#1^2". > > Am I doing something wrong, or is there a bug/problem with Mathematica. > > Regards, > Neil > > > > -- Solving a Three Equation ODE system (Linear with Constant > Coefficients) with Mathematica 3.0 ---- > > INPUT: > > DSolve[{y1'[x] + c11*y1[x] + c12*y2[x] +c13*y3[x] +c1==0, > y2'[x]+c21*y1[x]+c22*y2[x]+c23*y3[x]+c2==0, > y3'[x]+c31*y1[x]+c32*y2[x]+c33*y3[x]+c3==0, > y1[0]==y1i, y2[0]==y2i, y3[0]==y3i}, > {y1[x], y2[x], y3[x]}, x] > > OUTPUT: > > Eigensystem::"eivec": > "Unable to find eigenvector for eigenvalue \!\(Root[\(\(\(\(c13\\ > c22\\ \ > c31\) - \(c12\\ c23\\ c31\) - \(c13\\ c21\\ c32\) + \(c11\\ c23\\ c32\) + \ > \(\\[LeftSkeleton] 20 \\[RightSkeleton]\)\) &\), 1\)]\)." > Eigensystem::"eivec": > "Unable to find eigenvector for eigenvalue \!\(Root[\(\(\(\(c13\\ > c22\\ \ > c31\) - \(c12\\ c23\\ c31\) - \(c13\\ c21\\ c32\) + \(c11\\ c23\\ c32\) + \ > \(\\[LeftSkeleton] 20 \\[RightSkeleton]\)\) &\), 2\)]\)." > Eigensystem::"eivec": > "Unable to find eigenvector for eigenvalue \!\(Root[\(\(\(\(c13\\ > c22\\ \ > c31\) - \(c12\\ c23\\ c31\) - \(c13\\ c21\\ c32\) + \(c11\\ c23\\ c32\) + \ > \(\\[LeftSkeleton] 20 \\[RightSkeleton]\)\) &\), 3\)]\)." > General::"stop": > "Further output of \!\(Eigensystem :: \"eivec\"\) will be suppressed \ > during this calculation."