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Vector formulation of a system of ODEs for NDSolve

  • To: mathgroup at
  • Subject: [mg15551] Vector formulation of a system of ODEs for NDSolve
  • From: phillips at (Terry Phillips)
  • Date: Tue, 26 Jan 1999 13:44:35 -0500 (EST)
  • Organization: Los Alamos National Laboratory
  • Sender: owner-wri-mathgroup at

I would like to solve a system of differential equations with NDSolve,
using a vector equation to formulate the equations.  For example,
taking an problem from Chris Barkers excellent tutorial on solving
differential equations with Mathematica
( (thank you Chris!!)), the
system of differential equations:


is easily solved with NDSolve:



If I try to formulate this as a vector equation, where f[[1]]=x and
f[[2]]=y, and use the vector formulation in NDSolve,, I cannot find a
vector formulation of the problem that Mathematica will accept.  E.g.,


does not work, nor does:


Is there any way to formulate a system of differential equations in a
vector format for solution by NDSolve?  I am using Mathematica 3.0 with
Windows NT4.0.  Thank you for any help you can give me. Terry Phillips 
------  __o phillips at      -------  _`\<,_     Phone:
505 667-7379 US Mail: ESA-EPE, MS J576        ---- (*)/ (*)    FAX: 505
665-1323 Los Alamos National Laboratory                    Los Alamos,
NM 87545

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