Re: extracting contour points

*To*: mathgroup at smc.vnet.net*Subject*: [mg92491] Re: extracting contour points*From*: "David Park" <djmpark at comcast.net>*Date*: Wed, 1 Oct 2008 18:34:15 -0400 (EDT)*References*: <gbulri$ld4$1@smc.vnet.net>

I don't see two lines, but only one line. f[p_, a_, x_] = -p x + x^(a + 1); contourpoints = First[ContourPlot[ Arg[f[1, .6, x + I y]] == 0, {x, -2, 2}, {y, -2, 2}]] /. GraphicsComplex[pts_, data_] -> pts // Chop // Union {{1.00552, 0}, {1.01786, 0}, {1.02653, 0}, {1.02653, 0}, {1.05408, 0}, {1.07143, 0}, {1.10714, 0}, {1.12551, 0}, {1.14286, 0}, {1.17857, 0}, {1.21429, 0}, {1.25, 0}, {1.28571, 0}, {1.32143, 0}, {1.3398, 0}, {1.35714, 0}, {1.39286, 0}, {1.42857, 0}, {1.46429, 0}, {1.5, 0}, {1.57143, 0}, {1.64286, 0}, {1.71429, 0}, {1.78571, 0}, {1.85714, 0}, {2., 0}} ListPlot[contourpoints, Frame -> True, Axes -> False] -- David Park djmpark at comcast.net http://home.comcast.net/~djmpark/ "peterp" <peterp at m.njit.edu> wrote in message news:gbulri$ld4$1 at smc.vnet.net... > Hello all, > > I've searched the group but I still have a problem. The contour sought > below returns two lines (you can actually see them on the graphic output). > The commands after the contour plot only extract the coordinates of one > of the two lines. How do I get the second ? > I tried replacing "First" by "Second" but no dice. > > Thanks, > Peter > > f[p_, a_, x_] = - p x + x^(a + 1) > > contour = > ContourPlot[Arg[f[1, .6, x + I y]], {x, -2, 2}, {y, -2, 2}, Contours > -> {0}, > ContourShading -> False, PlotPoints -> 100] > > grcontour = Graphics[contour]; > InputForm[grcontour]; > lns = First[ > Cases[First[grcontour] // Normal, Line[pts_] -> pts, \ > [Infinity]]]; > dat = Table[lns]; > Export["junk.dat", Re[dat]] >