Re: Plot artifact of NDSolve result

*To*: mathgroup at smc.vnet.net*Subject*: [mg116142] Re: Plot artifact of NDSolve result*From*: DrMajorBob <btreat1 at austin.rr.com>*Date*: Thu, 3 Feb 2011 05:30:46 -0500 (EST)

This works: Clear[y] sol4 = NDSolve[{eqn4, y[0] == 0, y'[0] == 1}, y, {t, 0, 70}, WorkingPrecision -> 20, MaxStepSize -> 0.01]; y = y /. First@sol4; Plot[{y[t], y'[t], y''[t]}, {t, 0, 70}, PlotRange -> All, PlotPoints -> 100] PlotPoints had to be increased. Eliminating Evaluate and /.soln4 in the plot was mostly for style. Bobby On Wed, 02 Feb 2011 05:07:13 -0600, 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? > -- DrMajorBob at yahoo.com