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Parametric plots from NDSolve

  • To: mathgroup at smc.vnet.net
  • Subject: [mg16523] Parametric plots from NDSolve
  • From: Virgil Stokes <virgil.stokes at neuro.ki.se>
  • Date: Tue, 16 Mar 1999 04:00:02 -0500
  • Sender: owner-wri-mathgroup at wolfram.com

I have the following short piece of code for solving a system of 2 2nd order
nonlinear
differential eqs.

Clear[p,q,r,P,Q,R];

p = 2; q = 2; r = 2/3;
P = 2; Q= 4/3; R=-1;
f = x[t] (p-r x[t] - q y[t]);
g = y[t] (P-Q x[t] - R y[t]);
eq = {x''[t] == f, y''[t] == g, x[0] == x0, x'[0] == 0.0,y[0] == y0,
    y'[0] == 0.0};

sol = NDSolve[eq /. {x0->3.5, y0->2},{x[t],y[t]},{t,0,2}];


This codes works fine; but, I have been unable to figure out how
to plot:

    x'[t] vs y'[t]
          or
  x''[t] vs y''[t]

How can one obtain parametric plots for the derivatives?

-- V Stokes



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