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MathGroup Archive 2010

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ParametricPlot3D problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg110784] ParametricPlot3D problem
  • From: "Juan Fernando Herrera J." <juanfhj at gmail.com>
  • Date: Tue, 6 Jul 2010 05:02:32 -0400 (EDT)

I'm trying to plot electric field lines as tubes with a parametric
plot. I build a list with n points as

  ptsA = BuildPointList[th]

where th is the angle of the field line. ptsA[[1]] is then the list of
points, and ptsA[[2]], ptsA[[3]] are lists giving two vectors
perpendicular to the field line at each point.

I go on to define

F[pts_,i_,t_]:=pts[[1, i]] + pts[[2, i]] Cos[t] + pts[[3, i]] Sin[t]

When I plot with

ParametricPlot3D[
    F[ptsA, i, t],
    {i, 1, n , 1},
    {t, 0, 2 Pi}]

I obtain a field line as a tube. But when I try plotting two lines ptsA, ptsB as

ParametricPlot3D[
    {F[ptsA, i, t],
     F[ptsB, i, t]},
    {i, 1, n, 1},
    {t, 0, 2 Pi}]

I get ParametricPlot3D::ppfun: Argument {F[ptsA, i, t], F[ptsB, i, t]}
is not a list with three or four elements.

What's wrong here? Thanks

Juan Herrera


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