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MathGroup Archive 2004

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Re: Interpolating function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49186] Re: Interpolating function
  • From: Paul Abbott <paul at physics.uwa.edu.au>
  • Date: Tue, 6 Jul 2004 03:34:43 -0400 (EDT)
  • Organization: The University of Western Australia
  • References: <ccb6cc$eq4$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

In article <ccb6cc$eq4$1 at smc.vnet.net>,
 mathma18 at hotmail.com ("G.L.Narasimham") wrote:

> ODE=0==y''[t]+(1-y[t])/y'[t];
> NDSolve[{ODE,y[1]==1,y'[1]==1},y,{t,-2,3}];
> y2[u_] =  y[u] /. First[%];
> yd = Dt[y2[t],{t,1}]; ydd = Dt[y2[t],{t,2}];
> Plot[ {y2[t],y3[t],yd,ydd},{t, -2, 3 }];
> " Is it not possible to directly access
>  y'[t]and y''[t] plots without Dt? "

Yes it is. Use Evaluate:
   
  ODE=0==y''[t]+(1-y[t])/y'[t];

  nsol=NDSolve[{ODE,y[1]==1,y'[1]==1},y,{t,-2,3}];

  Plot[ Evaluate[{y[t], y'[t], y''[t]}/.nsol],{t, -2, 3 }]

Cheers,
Paul

-- 
Paul Abbott                                   Phone: +61 8 9380 2734
School of Physics, M013                         Fax: +61 8 9380 1014
The University of Western Australia      (CRICOS Provider No 00126G)         
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Crawley WA 6009                      mailto:paul at physics.uwa.edu.au 
AUSTRALIA                            http://physics.uwa.edu.au/~paul


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