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Re: ContourPlot confusion

  • To: mathgroup at smc.vnet.net
  • Subject: [mg116384] Re: ContourPlot confusion
  • From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
  • Date: Sat, 12 Feb 2011 05:21:28 -0500 (EST)
  • References: <ij2ukh$7im$1@smc.vnet.net>

I suppose it should evaluate to 0. If it's a wildly changing function
you may expect large values in the neighbourhood of this line. If you
would disclose your function there might be more to say here.

Cheers -- Sjoerd

On Feb 11, 10:13 am, kelly <kere... at gmail.com> wrote:
> Hi!  I'm plotting the following:
>
> ContourPlot[Expression[50, x, y] == 0), {x, -15, -17}, {y, -0.7, -0.5}]
>
> So some previously defined expression which is a function of 50, x, and y.  I've set it to only show the "Expression = 0" contour, which it does.  
>
> However, when I use "Get Coordinates" to get the coordinates of a point along this contour line & plug those coordinates back into the expression, it evaluates to around -33.  Shouldn't it evaluate to 0 if the point lies along the 0 contour?
>
> Any help is appreciated!  So confused!



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