Re: How display negative contours with dashed lines?
- To: mathgroup at smc.vnet.net
- Subject: [mg16868] Re: How display negative contours with dashed lines?
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Mon, 5 Apr 1999 02:24:15 -0400
- References: <7e1d1b$bd6@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
WOOD DAVID M <dmwood at slate.Mines.EDU> wrote in message news:7e1d1b$bd6 at smc.vnet.net... > Howdy all. > > Despite rooting around like a cyber-pig after Mathematica truffles > (with DejaNews, AltaVista, and on MathSource), I can find no > suggestions or even mention of something that I suspect isn't hard to > do [except for me :)] > > I'd like to produce contour plots for which NEGATIVE function values > are indicated as dashed lines, while other values use solid lines. > > Can anyone suggest how I can on-the-fly specify ContourStyle options > that will display negative contour values (say in ContourPlot or > ListContourPlot) as *dashed* lines, via (e.g.) Dashing [or in any > other way]? > > Many thanks! > -- > David M. Wood > Department of Physics, Colorado School of Mines, Golden, CO 80401 > Phone: (303) 273-3853; Fax: (303) 273-3840 > e-mail: dmwood at physics.Mines.EDU ; NeXTMail welcome > David: It will be simpler if we use a function: fn[x_,y_]:=x; cg=ContourPlot[fn[x,y], {x,-1,1},{y,-1,1}, Contours -> 2] This outputs a ContourGraphics object, which does not store lines and polygons (please check InputForm[cg]) Convert to a Graphics object, which does (please check InputForm) gr=Graphics[cg] Now adjust the contour lines and show Show[gr/.{dir___,ln_Line/;fn@@ln[[1,1]]<0}:> {dir,Hue[0], Thickness[.02],Dashing[{.05,.05}], ln}] 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