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non integer exponents in ContourPlot[]?

• To: mathgroup at smc.vnet.net
• Subject: [mg35209] non integer exponents in ContourPlot[]?
• From: "1.156" <rob at piovere.com>
• Date: Tue, 2 Jul 2002 02:12:11 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

Mathematica wizards all:

The following code runs fine, note the (apparent) floating point form of the exponents.

a=-5.75;b=2;d=1.1;

ContourPlot[a*((x^2.0 + y^2.0)^0.5 + b*y^2.0), {x, -d, d}, {y, -d, d}, ContourShading -> False,
   Contours -> {-6, -3, -1}, PlotPoints -> 30];

But, if I make any of the 2.0 exponents say, 2.1, I get big error messages like

ContourGraphics::ctpnt:
   The contour is attempting to traverse a cell in which some of the points have not evaluated to numbers,
    and it will be dropped.

However, it works fine if I change the 0.5 exponent to say, 0.55.

Can anyone give me a hint of what's going on here? I'd sure like to be able to play with these exponents to fit some data.

Thanks, Rob

• Follow-Ups:
  • Re: non integer exponents in ContourPlot[]?
    • From: Tomas Garza <tgarza01@prodigy.net.mx>