Re: problems with ContourPlot

• To: mathgroup at smc.vnet.net
• Subject: [mg33640] Re: problems with ContourPlot
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Thu, 4 Apr 2002 19:40:00 -0500 (EST)
• Organization: Universitaet Leipzig
• References: <a8g2l1\$b1g\$1@smc.vnet.net>
• Reply-to: kuska at informatik.uni-leipzig.de
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

you do this also in FORTRAN -- great ! But a power
in FORTRAN is denoted by a**b, in Mathematica a**b
is NonCommutativeMultiply, a power is denoted by a^b

Try

With[{a = 0.5, b = 0.5, c = 0.5, y = 0.0},
ContourPlot[(x*(x - a) + y*y + z*z)/(Sqrt[(x*x + y*y + z*z)^3]*
Sqrt[((x - a)^2 + y*y + z*z)^3]) - ((x - a)*(x - a - b - c)
+
y*y + z*z)/(Sqrt[((x - a)^2 + y*y + z*z)^3]*
Sqrt[((x - a - b - c)^2 + y*y + z*z)^3]) - (x*(x - a - b) +
y*y +
z*z)/(Sqrt[(x*x + y*y + z*z)^3]*
Sqrt[((x - a - b)^2 + y*y + z*z)^3]) + ((x - a - b)*(x - a -
b -
c) + y*y + z*z)/(Sqrt[((x - a - b)^2 + y*y + z*z)^3]*
Sqrt[((x - a - b - c)^2 + y*y + z*z)^3]), {x, -1, 1}, {z, 0,
1},
Contours -> {0, 1, 5, 10, 50, 100}, ContourShading -> False]
]

and all works fine.

Regards
Jens

Harald von der Osten-Woldenburg wrote:
>
> Hi out there,
>
> if I try this:
>
> a := 0.5; b := 0.5; c := 0.5; y := 0.0;
>
> ContourPlot[(x*(x - a) + y*y + z*z)/ (Sqrt[(x*x + y*y + z*z) ** 3]*
>           Sqrt[((x - a) ** 2 + y*y + z*z) ** 3]) - ((x - a)*(x - a - b
> -c) +
>           y*y + z*z)/ (Sqrt[((x - a) ** 2 + y*y + z*z) ** 3]*
>           Sqrt[((x - a - b - c) ** 2 + y*y + z*z) ** 3]) - (x*(x - a -b)
> +
>           y*y + z*z)/ (Sqrt[(x*x + y*y + z*z) ** 3]*
>           Sqrt[((x - a - b) ** 2 + y*y + z*z) **
>               3]) + ((x - a - b)*(x - a - b - c) + y*y +
>           z*z)/(Sqrt[((x - a - b) ** 2 + y*y + z*z) ** 3]*
>           Sqrt[((x - a - b - c) ** 2 + y*y + z*z) ** 3]), {x, -1, 1},
> {z, 0, 1}, Contours -> {0, 1, 5, 10, 50, 100}, ContourShading -> False]
>
> I receive the error-messages:
>
> [ ...Expression... ] is not a machine-size real number at {x, z} =
> {-1.,0.}
>
> 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."
>
> General::"stop": "Further output of (ContourGraphics :: "ctpnt") will be
> suppressed during this calculation."
>
> Because I compiled this also with Fortran I know that there are also
> results in the range up to 10^6. Is this too much for ContourPlot? Or
> did I some crazy things.... ?? At (-1,0.) I  cannot find any
> singularity...
>
> Thank you very much for any small hint.
>
> Harry
>
> --
> Harald von der Osten-Woldenburg
> Geophysical Prospection of Archaeological Sites
> National Heritage Department of Baden-Wuerttemberg
> Silberburgstrasse 193, D-70178 Stuttgart
> Fax Office: +49-(0)711-1694-707
> http://www.lb.netic.de/hvdosten : Geomagnetics, Geoelectrics, Radar, EMI

```

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