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Re: Plot artifact of NDSolve result

  • To: mathgroup at smc.vnet.net
  • Subject: [mg116119] Re: Plot artifact of NDSolve result
  • From: "Kevin J. McCann" <Kevin.McCann at umbc.edu>
  • Date: Thu, 3 Feb 2011 05:26:17 -0500 (EST)
  • References: <iibdt9$no5$1@smc.vnet.net>

This is because Mathematica did not use enough points. Try PlotPoints->100
or so in you plot.

Kevin

On 2/2/2011 6:07 AM, Bert RAM Aerts wrote:
> Both in Mathematica 8.0.0 and 7.0.1 the plot of NDSolve result is
> wrong near x-axis point 60. But when zooming in, plot is correct.
>
> Notebook and screenshot of result are available on http://users.skynet.be/fa991376/
>
> eqn4 = y''[t] == -y[t]^2 + t
>
> sol4 = NDSolve[{eqn4, y[0] == 0, y'[0] == 1}, y, {t, 0, 70},
>    WorkingPrecision ->  20, MaxStepSize ->  0.01]
>
> Below plot contains the artifact:
>
> Plot[Evaluate[{y[t], y'[t], y''[t]} /. sol4], {t, 0, 70},
>   PlotRange ->  All]
>
> Below plot is correct:
>
> Plot[Evaluate[{y[t], y'[t], y''[t]} /. sol4], {t, 50, 70},
>   PlotRange ->  All]
>
> Is there a way to avoid this?
>


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