Re: Contour Lines

*To*: mathgroup at smc.vnet.net*Subject*: [mg83592] Re: [mg83583] Contour Lines*From*: DrMajorBob <drmajorbob at bigfoot.com>*Date*: Sat, 24 Nov 2007 04:08:11 -0500 (EST)*References*: <20637792.1195837227004.JavaMail.root@m35>*Reply-to*: drmajorbob at bigfoot.com

f[x_, y_] := x^2 + 2 y^2 plot1 = ContourPlot[f[x, y], {x, -2, 2}, {y, -2, 2}, Contours -> {1}, ContourShading -> False, PlotPoints -> {30, 30}] lines = Cases[Normal@plot1, _Line, Infinity]; Graphics@lines Bobby On Fri, 23 Nov 2007 04:38:41 -0600, Wyn Evans <nwe at ast.cam.ac.uk> wrote: > > How do you extract the coordinates of points making up a Contour Line as > a List? > > This has been dealt with before in the archive (see e.g., [mg68657]) > but the code there seems no longer to work. For example, the following is > suggested > > f[x_, y_] := x^2 + 2y^2 > plot1 = ContourPlot[f[x, y], {x, -2, 2}, {y, -2, 2}, Contours -> {1}, > ContourShading -> False, PlotPoints -> {30, 30}]; > f[x_, y_] := x^2 + 2y^2 > plot1 = ContourPlot[f[x, y], {x, -2, 2}, {y, -2, 2}, Contours -> {1}, > ContourShading -> False, PlotPoints -> {30, 30}]; > > Convert the ContourGraphics to Graphics and then extract the first part > and you will see how Mathematica represents the contours. > > contour = First@Graphics@plot1 > (output omitted) > > > I can see that the data I want (the actual coordinates) is there, but I > can't figure how to extract it as a matrix or list. > > > > -- DrMajorBob at bigfoot.com