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MathGroup Archive 1998

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Re: ODEs and phase portraits

  • To: mathgroup at
  • Subject: [mg14773] Re: ODEs and phase portraits
  • From: Dr Phillip Kent <p.kent at>
  • Date: Sat, 14 Nov 1998 03:08:04 -0500
  • Organization: Imperial College
  • References: <728kp1$> <72fad6$feq$>
  • Sender: owner-wri-mathgroup at

Kevin J. McCann wrote:
> Try this one:
>  ...............................
> phantomlord at wrote in message <728kp1$ehc at>...
> >I am trying to write a function such that I have the following ODE:
> >x''(t)+epsilon*(x(t)^2-1)*x'(t)+x(t)==0  [1] where epsilon is to be one
> >of the parameters in the function. I want to beable to draw out the
> >phase portraits for the equation for different values of epsilon.
> >
> ..............................
> >Perhaps there is a built in function that will allow me to do this? If
> >not do, can anybody suggest another way to do this?
> >
> >Also after plotting the trajectory is there any way to determine the
> >direction of it in Mathematica?
> >
> >thanks for you time.
> >Paul
> >

I have prepared a little code package to make trajectories and  phase
portraits easier to handle - please take a look:

 Dr Phillip Kent                  | tel: +44 (0)171 594 8503  
 The METRIC Project               | fax: +44 (0)171 594 8517
 Mathematics Department           | 
 Imperial College                 | p.kent at 
 London SW7 2BZ, U.K.             |
      "In designing tools we are designing ways of being"

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