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How to render level curves in several colors.

David Barnes, retired
Posted 4 years ago

I have a function of two variables defined on a region D in the x-y plane and I am looking at the contour curves of the form f(x,y)=cnst for several different constants. I am using the command ContourPlot[.....] to plot the function and it's level curves and I would like to render the level curves in different colors. Alas, the function RGBColor[...] is not an option for ContourPlot[.....]. Is there any other way to render the level curves in a chosen color? As an example, I have the following code.

a=0;b=1;c=0;d=2;
f[x_,y_]=Sin[Pi x]^2 Sin[Pi y]^2;

ContourPlot[f[x,y],{x,a,b},{y,c,d},
      ContourShading->False,
      AspectRatio->Automatic,
      Contours->{0,.2,.5,.7,.9},
      PlotPoints->100,
      AspectRatio->1,
      DisplayFunction->$DisplayFunction];
POSTED BY: David Barnes
8 Replies
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I see that you have succeded in doing what I want to do. But when I try to use your code on my machine it does not work correctly. I am attaaching my code as a file if you want to look at it I would be most greatful. Dave Barnes.

Attachments:
contours.nb
POSTED BY: David Barnes

Hi David,

the code still exhibits the missing 'R' typo in one of the RGBColor heads. Furthermore, you appear to be using Mathematica version 5.2.

We may be looking at a bug that's 10 years or older.

It that's so, the following code may be a work-around.

Show@MapThread[ ContourPlot[f[x, y], {x, a, b}, {y, c, d}, ContourShading -> False, AspectRatio -> Automatic, Contours -> {#1}, PlotPoints -> 100, ContourStyle -> #2, AspectRatio -> 1] &, {{0, .5, .7, .9}, {RGBColor[0, 0, 0], RGBColor[1, 1, 0], RGBColor[0, 1, 0], RGBColor[0, 0, 1]}} ]
POSTED BY: Markus van

(* Sorry about the mixup in the code the I posted. The cut and paste function somehow missed up the translation and left out a bunch of stuff. I think this post is correct. It shows my problem with the colors of the level curves. *) a = 0; b = 1; c = 0; d = 2; f[x, y] := Sin[Pi x]^2 Sin[Pi y]^2;

  p1 = ContourPlot[f[x, y], {x, a, 
          b}, {y, c, d}, ContourShading -> False, AspectRatio -> Automatic, 
  Contours -> {.7}, PlotPoints -> 100, ContourStyle -> RGBColor[1, 0, 1],
        AspectRatio -> 1];

  p2 = ContourPlot[f[x, y], {x, a, b}, {y, c, d}, ContourShading -> 
        False, AspectRatio -> Automatic, Contours -> {.9}, PlotPoints -> 
          100, ContourStyle -> RGBColor[1, 0, 1],
        AspectRatio -> 1];

  p3 = ContourPlot[f[x, 
        y], {x, 0, 1}, {y, 0, 2}, ContourShading -> None, AspectRatio -> 
  Automatic, Contours -> {0, .5, .7, .9}, PlotPoints -> 100,
      ColorFunction -> {RGBColor[0, 0, 0], RGBColor[1, 1, 0], RGBColor[
        0, 1, 0], GBColor[0, 0, 1]}, 
          ContourStyle -> {RGBColor[0, 0, 0], RGBColor[1,
           1, 0], RGBColor[0, 1, 0], GBColor[0, 0, 1]},
      AspectRatio -> 1]
POSTED BY: David Barnes
Rohit Namjoshi
Rohit Namjoshi
Posted 4 years ago

Typo GBColor should be RGBColor. AspectRatio is specified twice, earlier one takes precedence.

ContourPlot[f[x, y], {x, 0, 1}, {y, 0, 2},
 ContourShading -> None,
 AspectRatio -> Automatic,
 Contours -> {0, .5, .7, .9},
 ContourStyle -> {RGBColor[0, 0, 0], RGBColor[1, 1, 0], RGBColor[0, 1, 0], RGBColor[0, 0, 1]}]

enter image description here
POSTED BY: Rohit Namjoshi
Yasmin Hussain
Yasmin Hussain
Posted 4 years ago

Can I know the output? I mean I am interested in this, but I wanna see the output. :)
POSTED BY: Yasmin Hussain

(* Here is some code that shows my problem witn=h cotour colors. The cut and paste function did not work right in my revious post *) a = 0; b = 1; c = 0; d = 2; f[x, y] := Sin[Pi x]^2 Sin[Pi y]^2; p1 = ContourPlot[f[x, y], {x, a, b}, {y, c, d}, ContourShading -> False, AspectRatio -> Automatic, Contours -> {.7}, PlotPoints -> 100, ContourStyle -> RGBColor[1, 0, 1], AspectRatio -> 1]; p2 = ContourPlot[f[x, y], {x, a, b}, {y, c, d}, ContourShading -> False, AspectRatio -> Automatic, Contours -> {.9}, PlotPoints -> 100, ContourStyle -> RGBColor[1, 0, 1], AspectRatio -> 1]; p3 = ContourPlot[f[x, y], { x, 0, 1}, {y, 0, 2}, ContourShading -> None, AspectRatio -> Automatic, Contours -> {0, .5, .7, .9}, PlotPoints -> 100, ContourStyle -> { RGBColor[0, 0, 0], RGBColor[1, 1, 0], RGBColor[0, 1, 0], GBColor[0, 0, 1]}, AspectRatio -> 1]
POSTED BY: David Barnes
Updating Name
Updating Name
Posted 4 years ago

Adding the command "ContourStyle -> {Red, Blue, Green, Yellow, Orange} " To my code results in a plot of the contour curves that are all orange colored. They are not {Red, Blue, Green, Yellow, Orange} in that order.
POSTED BY: Updating Name

Consider using the Option ContourStyle:

Clear[f];
f[x_, y_] := Sin[Pi x]^2 Sin[Pi y]^2;

ContourPlot[
    f[x, y], 
    {x, 0,1}, {y, 0,2}, 
    ContourShading -> None, 
     AspectRatio -> Automatic, Contours -> {0, .2, .5, .7, .9}, 
     PlotPoints -> 100, AspectRatio -> 1, 
     ContourStyle -> {Red, Blue, Green, Yellow, Orange}
]
POSTED BY: Markus van
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