MATLAB Central Newsreader - colors for contour plots

colors for contour plots

Ernesto molina — Wed, 23 Sep 2009 07:00:07 -0400

hi there,
I.m doing some contour plots (contourf) and I will llike to assign specific colors for value ranges....the colormap editor does not allow me to choose specificly that I want for example:
dark red: > +12.5m
mid red: +7.5 < X <= +12.5 m
light red: +2.5 m < X <= +7.5 m

any help will be very appreciated
Cheers
Ernesto

Re: colors for contour plots

Sebastiaan — Wed, 23 Sep 2009 10:09:04 -0400

"Ernesto molina" <onka72@hotmail.com> wrote in message <h9ch1n$121$1@fred.mathworks.com>...
> hi there,
> I.m doing some contour plots (contourf) and I will llike to assign specific colors for value ranges....the colormap editor does not allow me to choose specificly that I want for example:
> dark red: > +12.5m
> mid red: +7.5 < X <= +12.5 m
> light red: +2.5 m < X <= +7.5 m
>
> any help will be very appreciated
> Cheers
> Ernesto

As far as I know, you can only change the contour fill colour afterwards, not specify it while plotting.

Example using peaks:
[C,h] = contourf(peaks(20));
Cld = get(h, 'Children');
for j=1:length(Cld)
    if strcmp(get(Cld(j), 'Type'), 'patch')
        Iso = get(Cld(j), 'CData');
        if Iso<-5
            set(Cld(j), 'FaceColor', [1 0 0]);
        elseif Iso>=-5 && Iso<0
            set(Cld(j), 'FaceColor', [0 1 0]);
        elseif Iso>=0 && Iso<5
            set(Cld(j), 'FaceColor', [0 0 1]);
        else
            set(Cld(j), 'FaceColor', [0 1 1]);
        end
    end
end

Will this work for you?

Sebastiaan

Re: colors for contour plots

Jerome Briot — Wed, 23 Sep 2009 11:58:06 -0400

> As far as I know, you can only change the contour fill colour afterwards, not specify it while plotting.
> ...
> Sebastiaan

The same solution but with a colormap :

figure

map = [1 0 0
       0 1 0
       0 0 1
       0 1 1];

colormap(map);

[C,h] = contourf(peaks(20));
Cld = get(h, 'Children');
for j=1:length(Cld)
    if strcmp(get(Cld(j), 'Type'), 'patch')
        Iso = get(Cld(j), 'CData');
        if Iso<-5
            set(Cld(j), 'cdata', 0);
        elseif Iso>=-5 && Iso<0
            set(Cld(j), 'cdata', 1);
        elseif Iso>=0 && Iso<5
            set(Cld(j), 'cdata', 2);
        else
            set(Cld(j), 'cdata', 3);
        end
    end
end

Jerome

Re: colors for contour plots

Ernesto molina — Thu, 24 Sep 2009 03:56:04 -0400

Thanks for that, I'm closer to get what a wanted but:
map =

         0 0 0.5608
         0 0.2510 1.0000
         0 1.0000 1.0000
    1.0000 1.0000 1.0000
    1.0000 0.3765 0
    1.0000 0 0
    0.7843 0 0

creating my 7 colors (range)
then colormap(map)
...[C,h] = contourf(long, time,'my variable');% my variable is 540x128
Cld = get(h, 'Children');
for j=1:length(Cld)
if strcmp(get(Cld(j),'Type'),'patch')
Iso=get(Cld(j),'CData');
if Iso > 12.5
set(Cld(j),'cdata',5);
elseif Iso >7.5&& Iso <= 12.5
set(Cld(j),'cdata',4);
elseif Iso >2.5&& Iso <= 7.5
set(Cld(j),'cdata',3);
elseif Iso >= -2.5 && Iso <= 2.5
set(Cld(j),'cdata',0);
elseif Iso < -2.5 && Iso >= -7.5
set(Cld(j),'cdata',1);
elseif Iso < -7.5 && Iso >= -12.5
set(Cld(j),'cdata',2);
elseif Iso < -12.5
end
end
end

..what I dont get is where you assign the color, I mean when doing set(Cld(j),'cdata', #).
I hope you understand my sort of explanation
cheers and thank you again
Ernesto
"Jerome Briot" <dut@matlab.fr> wrote in message <h9d2gd$76h$1@fred.mathworks.com>...
> > As far as I know, you can only change the contour fill colour afterwards, not specify it while plotting.
> > ...
> > Sebastiaan
>
> The same solution but with a colormap :
>
> figure
>
> map = [1 0 0
> 0 1 0
> 0 0 1
> 0 1 1];
>
> colormap(map);
>
> [C,h] = contourf(peaks(20));
> Cld = get(h, 'Children');
> for j=1:length(Cld)
> if strcmp(get(Cld(j), 'Type'), 'patch')
> Iso = get(Cld(j), 'CData');
> if Iso<-5
> set(Cld(j), 'cdata', 0);
> elseif Iso>=-5 && Iso<0
> set(Cld(j), 'cdata', 1);
> elseif Iso>=0 && Iso<5
> set(Cld(j), 'cdata', 2);
> else
> set(Cld(j), 'cdata', 3);
> end
> end
> end
>
> Jerome

Re: colors for contour plots

Rune Allnor — Thu, 24 Sep 2009 07:16:43 -0400

On 23 Sep, 09:00, "Ernesto molina" <onk...@hotmail.com> wrote:
> hi there,
> I.m doing some contour plots (contourf) and I will llike to assign specific colors for value ranges....the colormap editor does not allow me to choose specificly that I want for example:
> dark red: > +12.5m
> mid red: +7.5 < X <= +12.5 m
> light red: +2.5 m < X <= +7.5 m

First of all, set up a color map for the colors you want:

ncolors = 5;
cmap =zeros(ncolors,3);
cmap(:,1)=1;
cmap(:,2:3)=flipud((0:(ncolors-1))'*[1,1]/(ncolors-1));

Then plot the data with specified contour levels (note that
you need as many contour levens as colors in the color map):

data=rand(10);
contourf(data,[0,1,2]/3)

Last, activate the color map you made:

colormap(cmap)

And ther you are.

Rune