AW: ContourPlots,DensityPlots

*To*: mathgroup at smc.vnet.net*Subject*: [mg23612] AW: [mg23558] ContourPlots,DensityPlots*From*: Wolf Hartmut <hwolf at debis.com>*Date*: Wed, 24 May 2000 02:16:12 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

-----Ursprüngliche Nachricht----- Von: Paul Hoke [SMTP:hokepaul at pilot.msu.edu] Gesendet am: Samstag, 20. Mai 2000 09:11 An: mathgroup at smc.vnet.net Betreff: [mg23558] ContourPlots,DensityPlots 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? Dear Paul, I needed some guessing . . . but perhaps this example might help you: Let's define some data data = Table[Sin[x y] Cos[x] + 2, {y, 0, Pi, 0.2}, {x, 0, 2Pi, 0.2}]; {Min[data], Max[data]} {1.00674, 2.9862} (roughly between 1 and 3) We color the density plot in a certain way p = ListDensityPlot[data, MeshRange -> {{0, 2 Pi}, {0, Pi}}, ColorFunction -> (Hue[#/3] &), ColorFunctionScaling -> False] So 1 corresponds to Hue[1/3] (green) and 3 corresponds to Hue[1] (red), all other values are in between (blue, violet, no yellow or orange). This is reflected by the legend: << Graphics`Legend` ShowLegend[ p, {Hue[(2 # + 1)/3]&, 5, " 1", "3", LegendPosition -> {1.1, -.4}}] Why that (seemingly) different color function? within the legend the color function is probed between 0 and 1 (in 5 steps here). So all we have to do is to linearly map the interval {0, 1} to {min, max} of our applied color function (when ColorFunctionScaling -> False). So if you prefer to have the color scale at the legend reversed just do ShowLegend[ p, {Hue[(3 - 2 #)/3]&, 7, " 3", "1", LegendPosition -> {1.1, -.4}}] Kind regards, Hartmut