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]]
>