Re: ContourPlot and finite approximation to level sets

*To*: mathgroup at smc.vnet.net*Subject*: [mg68638] Re: ContourPlot and finite approximation to level sets*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>*Date*: Mon, 14 Aug 2006 06:44:09 -0400 (EDT)*Organization*: The Open University, Milton Keynes, UK*References*: <ebmu7p$6q9$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

dkjk at bigpond.net.au wrote: > Hi all, > > Given a real-valued function f(x,y) over {(x,y) | xmin < x < xmax, ymin > < y < ymax}, ContourPlot can be used to generate the graph of the level > set { (x,y) | f(x,y) = c } using > > ContourPlot[f[x,y],{x,xmin,xmax},{y,ymin,ymax},Contours->{c},ContourShading->False]. > > Is there any way to access the coordinates used by Mathematica to paint > the contour line of height c? If not, can anyone suggest an algorithm, > such as the one used by Mathematica, to finitely approximate a level > set? Hi James, The array of points (by default 25x25 points)is the first element of the SurfaceGraphics object return by ContourPlot. For example, cp = ContourPlot[Sin[x*y], {x, -1, 1}, {y, -1, 1}, Contours -> {0.5}, ContourShading -> False]; FullForm[cp] Dimensions[cp[[1]]] Best regards, Jean-Marc