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MathGroup Archive 1997

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Re: Mathematica Graphics

  • To: mathgroup at smc.vnet.net
  • Subject: [mg9023] Re: Mathematica Graphics
  • From: tharter at nswc.navy.mil (Terry Harter)
  • Date: Wed, 8 Oct 1997 00:05:21 -0400
  • Organization: Naval Surface Warfare Center, Dahlgren Division
  • Sender: owner-wri-mathgroup at wolfram.com

David Djajaputra wrote;
=========================
Could anyone tell me how to make Mathematica plot the following function
smoothly?

Wbar[q_,w_]:=w/(4 Sin[q/2]);

Chi[q_,w_]:=
  EllipticF[Pi/2 - ArcSin[Wbar[q,w]], 1/(1-Wbar[q,w]^2)]  /
Sqrt[1-Wbar[q,w]^2];

ChiPlot[q_,w_]:=
  If[(w>2 Sin[q])&&(w < 4 Sin[q/2]), Chi[q,w]/(2 Pi Sin[q/2]),0];

Plot[{ChiPlot[0.025,w]},{w,0.04999,0.050},PlotPoints->200,
  PlotRange->{19.998,20.003}]

If I run the last Plot command, Mathematica always complains about
ChiPlot[w] not being a machine-size real number at some points, and then
it only plots several disconnected lines. I realize the function is
rather `dangerous' but analytically  I expect it  to behave normally
inside the region that I use above, except perhaps at the
boundaries. Anyway, if Mathematica can get the separate lines, why can't
it obtain
the values for points between the lines also?

Much thanks in advance,

David Djajaputra
=====================
  Whenever I get such messages from the kernal, *I* always
check for unbalanced square braketws, paranthesis, list brackets, etc.
   Examinbe your definition of Chi[ ] -- I think it needs a "]" at the
end of its definition.
Hope this helps
....Terry


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