Re: ContourPlots,DensityPlots

• To: mathgroup at smc.vnet.net
• Subject: [mg23615] Re: ContourPlots,DensityPlots
• From: "Atul Sharma" <atulksharma at yahoo.com>
• Date: Wed, 24 May 2000 02:16:16 -0400 (EDT)
• Organization: McGill University
• References: <8g5frm\$gbq@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Bob Hanlon's answer as usual is concise and effective. One objection that I
have had to using the color function Hue is that Hue[0] and Hue[1] both
appear as red, which confuses (me at least). For this reason, I usually
replace Hue[#] with Hue[1-#/2], so as to assign unique colors. Modifying
Bob's solution to accomodate this minor prejudice of my own gives the
following, which scales your contours between blue and red. A similar
scaling could be accomplished with RGBColor[0.3+ 0.7 #, 0.4, 0.8]

I found Chapter 4 in Stan Wagon's book an excellent introduction to these
color scales. HTH.

A.S. :

Needs["Graphics`Legend`"]
data = Table[
10.*Sin[x + y]Cos[x - y], {x, xmin = -Pi, xmax = Pi, Pi/24.}, {y,
ymin = -Pi, ymax = Pi, Pi/24.}];
Plot3D[10Sin[x + y]Cos[x - y], {x, xmin, xmax}, {y, ymin, ymax},
PlotPoints -> 25];
ShowLegend[
ListContourPlot[data, ColorFunction -> (Hue[1 - #/2] &), Contours -> 12,
ContourLines -> False, DisplayFunction -> Identity], {Hue[1 - #/2] &,
11, ToString[Max[data]], ToString[Min[data]],
LegendPosition -> {1.1, -.4}}];
ShowLegend[
ListDensityPlot[data, ColorFunction -> (Hue[1 - #/2] &), Mesh -> False,
DisplayFunction -> Identity], {Hue[1 - #/2] &, 11,
ToString[Max[data]],
ToString[Min[data]], LegendPosition -> {1.1, -.4}}];

--
-------------------------------------------------------------------------
Atul Sharma MD, FRCP(C)
Pediatric Nephrologist,
McGill University/Montreal Children's Hospital

Paul Hoke wrote in message <8g5frm\$gbq at smc.vnet.net>...
>
>Anybody have a lot of experience with ListContourPlot and
>ListDensityPlot?
>
>I have a matrix of data I want to plot and show for a presentation.
>
>The problems I am having are as follows
>
>with ColorFunctionScaling->True, It doesn't seem that the colors have
>any thing to do with the actual values if I use a legend and use
>ColorFunction->Hue, the scale is on the plot doesn't equal the legend
>since the data is truncated to fit 0-1.
>
>I'm trying to divide by the largest value since all my data is positive
>and then the legend color scheme should fit the data plot except I don't
>have a zero in my data to peg the lower end.  I hate to add a zero in my
>matrix just to fix the lower end of the color scheme, is that the only
>option?
>
>I can delineate which contours I want, but I can't label them.  Is there
>anyway to print the value of contours?  That is on the plot have each
>contour marked so that it isn't just a bunch of lines?
>
>Paul
>
>
>________________________________
>Paul Hoke
>A107 Research Complex Engineering
>Michigan State University
>East Lansing MI 48824
>
>Hokepaul at egr.msu.edu
>Office 517.353.9952
>Lab 517.353.6434
>Fax 517.353.7179
>

```

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