Re: NDolve + ParametricPlot
- To: mathgroup at smc.vnet.net
- Subject: [mg67533] Re: [mg67513] NDolve + ParametricPlot
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Fri, 30 Jun 2006 04:13:57 -0400 (EDT)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
sol = NDSolve[{x''[t] == x[t], x[0] == 1, x'[0] == 1.1}, x, {t, 0, 3}]; Plot[x[t] /. sol, {t, 0, 3}]; Plot[D[x[t]] /. sol, {t, 0, 3}]; ParametricPlot[{x[t] , D[x[t]]}/.sol, {t, 0, 3}]; The exact solution is x[t]/.DSolve[{x''[t] == x[t], x[0] == 1, x'[0] == 11/10}, x[t], t][[1]] ((1/20)*(-1 + 21*E^(2*t)))/E^t %//FullSimplify Cosh[t] + (11*Sinh[t])/10 Bob Hanlon ---- Paolo Pani <paolopani at RIMUOVEREgmail.com> wrote: > Hi, i'm new with Mathematica..i'm getting mad with expressions like this: > > sol = NDSolve[{x''[t] == x[t], x[0] == 1, x'[0] == 1.1}, x, {t, 0, 3}]; > Plot[x[t] /. sol, {t, 0, 3}]; > Plot[D[x[t]] /. sol, {t, 0, 3}]; > ParametricPlot[Evaluate[{x[t] /. sol, D[x[t] /. sol]}], {t, 0, 3}]; > > The first two Plots are ok, the third give me: > > > > ParametricPlot::pptr: {InterpolatingFunction[{{0., 3.}}, {2, 2, True, > Real, \ > {3}, {0}}, {{\[LeftSkeleton]1\[RightSkeleton]}}, {{0, 3, 6, 9, 12, 15, 18, \ > 21, 24, 27, \[LeftSkeleton]32\[RightSkeleton]}, {1., 1.1, \[LeftSkeleton]8\ > \[RightSkeleton], \[LeftSkeleton]113\[RightSkeleton]}}, {Automatic}][t]} > does \ > not evaluate to a pair of real numbers at t = 1.25`*^-7. > > > > > ... and "More..." does tell nothing more. > > Where is my mistake? > > Thanks and sorry for my bad english > > Paolo >