problems with ContourPlot

*To*: mathgroup at smc.vnet.net*Subject*: [mg33616] problems with ContourPlot*From*: Harald von der Osten-Woldenburg <hvdosten at lb.netic.de>*Date*: Wed, 3 Apr 2002 18:08:22 -0500 (EST)*Organization*: LF.net GmbH, Stuttgart, Germany*Sender*: owner-wri-mathgroup at wolfram.com

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