Re: Plot artifact of NDSolve result

*To*: mathgroup at smc.vnet.net*Subject*: [mg116141] Re: Plot artifact of NDSolve result*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Thu, 3 Feb 2011 05:30:35 -0500 (EST)

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]; Change (increase) the number of initial sample points (PlotPoints). Plot[Evaluate[{y[t], y'[t], y''[t]} /. sol4], {t, 0, 70}, PlotRange -> All, ImageSize -> 400, PlotPoints -> 25] Bob Hanlon ---- Bert RAM Aerts <bert.ram.aerts at gmail.com> 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?