Re: DSolve for a system of 3 equations
- To: mathgroup at smc.vnet.net
- Subject: [mg36318] Re: DSolve for a system of 3 equations
- From: Neil Klepeis <nklepeis at uclink4.berkeley.edu>
- Date: Sat, 31 Aug 2002 01:26:02 -0400 (EDT)
- Organization: Lawrence Berkeley National Laboratory
- References: <akkctj$81o$1@smc.vnet.net> <akn0f8$lkv$1@smc.vnet.net>
- Reply-to: nklepeis at uclink4.berkeley.edu
- Sender: owner-wri-mathgroup at wolfram.com
Guillermo, Thanks for the package. I am also doing compartmental modeling, for indoor air exposure to particulate matter. Does your package use Runge-Kutta or some other numerical algorithm? I'm thinking of something like that, but with a fixed (non-adaptive) step size. Neil Guillermo Sanchez wrote: > 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." > > -- ______________________________________________________ Neil E. Klepeis, UC Berkeley, School of Public Health, and Lawrence Berkeley National Laboratory, Berkeley, CA USA. Voice: 831-768-9510