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MathGroup Archive 2007

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Re: ImplicitPlot errors

  • To: mathgroup at smc.vnet.net
  • Subject: [mg75097] Re: ImplicitPlot errors
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Mon, 16 Apr 2007 20:21:11 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <evvbfs$9q5$1@smc.vnet.net>

David Rees wrote:
> Hi,
> 
> I've been trying to get ImplicitPlot to plot an implicit function (naturally 
> ;) ), but it throws errors to cryptic for me, even when copying and pasting 
> from the Mathematica function reference.
> 
> In[40]:= ImplicitPlot[{x^2 + x*y + y^2 == 7, y == 2*Sqrt[7/3]}, {x, -5, 5}]
> 
> ImplicitPlot::var :
> 
> Equation x^2+x 
> Function[x,x^2+2xy-3y^2-16]+Function[x,x^2+2xy-3<<1>>-16]^2==7 does not have 
> a single variable other than x
> 
> ImplicitPlot::var :
> 
> Equation Function[x,x^2+2xy-3y^2-16]==2Sqrt(7/3) does not have a single 
> variable other than x
> 
> Out[40]:=\!\(ImplicitPlot[{x\^2 + x\ Function[x, x\^2 + 2\
>           xy - 3\ y\^2 - 16] + Function[
>               x, x\^2 + 2\ xy - 3\ y\^2 - 16]\^2 == 7, Function[x, x\^2 + 2\
>               xy - 3\ y\^2 - 16] == 2\ \@\(7\/3\), x == 2\ \@\(7\/3\)}, {x, 
> \
> \(-5\), 5}, {Function[x, x\^2 + 2\ xy - 3\ y\^2 - 16], \(-5\), 5}]\)
> 
> 
> 
> What am I doing wrong? Even ImplicitPlot[x+y==2,{x,-4,4}] fails.
> 
> Thanks

You must have written (or loaded) some conflicting definitions before 
using *ImplicitPlot*. Try a fresh session. The following works fine on 
my system:

In[1]:=
Remove[ImplicitPlot, x, y]
Needs["Graphics`ImplicitPlot`"]
ImplicitPlot[{x^2 + x*y + y^2 == 7, y == 2*Sqrt[7/3]}, {x, -5, 5}]
ImplicitPlot[x + y == 2, {x, -4, 4}]

(* A straight line and a ellipse are plotted *)
Out[3]=
â??Graphicsâ??

(* A inclined straight line is plotted *)
Out[4]=
â??Graphicsâ??

Regards,
Jean-Marc


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