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I'm trying to plot the solution of an equation using NDSolve. For some reason nothing shows up in the plot. I checked the output of the interpolating function and it doesn't look like there is anything wrong with the data - though I could be wrong - so I'm just trying to figure out what is going on.

     q2 = NDSolve[{u'[ϕ] == -Sqrt[3 - 2 u[ϕ] ArcSech[1/u[ϕ]]/Sqrt[u[ϕ]^2 - 1]], 
                  u[1.494706195984861] == 3.208921901232091}, 
                  u, {ϕ, 1.494706195984861, 20}]

Then when I use PolarPlot to plot the function, nothing appears:

s2 = PolarPlot[Evaluate[1/u[ϕ] /. q2], {ϕ, 1.494706195984861, 14.708465676522565},
               PlotRange -> All, PlotStyle -> Thick]

Thanks in advance for any help.

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closed as off-topic by Sjoerd C. de Vries, m_goldberg, bobthechemist, C. E., rm -rf Jan 25 '14 at 14:48

This question appears to be off-topic. The users who voted to close gave this specific reason:

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  • 2
    $\begingroup$ it is complex. Try s2 = PolarPlot[Evaluate[Re[1/u[\[Phi]] /. q2]], {\[Phi], 1.494706195984861, 14.708465676522565}, PlotRange -> All, PlotStyle -> Thick] !Mathematica graphics $\endgroup$ – Nasser Jan 24 '14 at 17:42
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    $\begingroup$ And the imaginary part isn't negligible ... $\endgroup$ – Dr. belisarius Jan 24 '14 at 17:47
  • $\begingroup$ @Nasser, Thank you! $\endgroup$ – Nicole Jan 26 '14 at 19:15
  • $\begingroup$ @belisarius, Thanks! $\endgroup$ – Nicole Jan 26 '14 at 19:16
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As pointed out in the comments, your result is complex. You could split real and imaginary part and plot them together:

PolarPlot[Evaluate[{Re[#], Im[#]} & @@ (1/u[\[Phi]] /. q2)], 
  {\[Phi], 1.494706195984861, 14.708465676522565}, 
  PlotRange -> All, PlotStyle -> Thick]

Mathematica graphics

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  • $\begingroup$ Perfect. Thank you! $\endgroup$ – Nicole Jan 26 '14 at 19:14

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