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? >