Re: 3D contour through a point

*To*: mathgroup at smc.vnet.net*Subject*: [mg34025] Re: 3D contour through a point*From*: "Allan Hayes" <hay at haystack.demon.co.uk>*Date*: Sat, 27 Apr 2002 00:56:28 -0400 (EDT)*References*: <aab00u$mdl$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Bram, I use ContourPlot for convenience: g=ContourPlot[Sin[x]+y,{x,0,Pi},{y,0,1},Contours->{Sin[.6]+.2}, ContourShading->False ] The above gives ContourGraphics object that does not contin the contour lines explicitely - they areconstructed for each display. Convert to a Graphics object that does contain the lines. g2=Graphics[g] Delete lines that do not contain a point close enough to {.6,.2} g3=DeleteCases[g2,ln_Line/;Min[(#.#&[{.6,.2}-#])&/@ln[[1]]]<0.1, Infinity]; Show[g3]; We can extract the line Cases[g3,ln_Line,Infinity] This technique could stand some refinement, and, if you wish to work interactively you could extract all the contour lines: Cases[g2,ln_Line,Infinity] and pick the one you want by inspection. -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 "Bram Platel" <b.platel at stud.tue.nl> wrote in message news:aab00u$mdl$1 at smc.vnet.net... > I would like to make a contourplot of a 3D data set, but not from all the > same gray levels in the image (as is default now) but I only want to plot a > contour surface that goes through one point in the 3D data set. > > For example, if I have a 3D dataset (e.g. a 3D image) and I plot a 3D > contour of the gray value in pixel (x,y) then I could get a couple of > contour surfaces which are not connected to each other and only one of them > goes through point (x,y). > But what I want is only a contour surface that goes through this point > (x,y). So that I can plot a contour that belongs to a point (and it's gray > value). > > Any advice on this? > > Thanks, > Bram > > >