Re: NDolve + ParametricPlot
- To: mathgroup at smc.vnet.net
- Subject: [mg67544] Re: NDolve + ParametricPlot
- From: bghiggins at ucdavis.edu
- Date: Fri, 30 Jun 2006 04:14:34 -0400 (EDT)
- References: <e7vkhi$sjo$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Paolo, You have an extra set of braces. Use Flatten to get rid of the extra set of braces: ParametricPlot[Flatten[Evaluate[{x[t] /. sol, D[x[t] /. sol]}]], {t, 0, 3}] Cheers, Brian Paolo Pani 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