How to handle a colormap with multiple patches?

Hello Matlab-Pros

I have a program that should mark certain elements of 3 different graphs if special conditions are met. This conditions can lead to 3 different colors.

To do this I use a custom colormap with exactly 3 colors. If the input actually needs all of this colors it works fine, but if it only needs one color it always uses the middle one.

I put the essential part of the program in the attached script, this should make my problem clear.

How can I always get the colors right?

Best regards and thanks in advance,

Michael

% This one works: (1 = red, 2 = orange, 3 = yellow)
areas = [54 134 1; 354 701 2; 2913 3687 3];

% In case the three patches have the same color it doesn't work: (all should be red)
areas = [54 134 1; 354 701 1; 2913 3687 1];


% Create Figure and Axes
Figure = figure;

subAx1 = subplot(1,3,1);
subAx2 = subplot(1,3,2);
subAx3 = subplot(1,3,3);


xlimit1 = [0.3 0.8];
xlimit2 = [20 50];
xlimit3 = [0 10000];

% This part rearranges 'areas' and 'xlimits' to a way, that 'patch' can work with it
areas(:,1:2) = (areas(:,1:2) - 1)/100;
x1 = repmat([xlimit1(1) xlimit1(2) xlimit1(2) xlimit1(1)],size(areas,1),1)';
x2 = repmat([xlimit2(1) xlimit2(2) xlimit2(2) xlimit2(1)],size(areas,1),1)';
x3 = repmat([xlimit3(1) xlimit3(2) xlimit3(2) xlimit3(1)],size(areas,1),1)';
y = repelem(areas(:,1:2)',2,1);


% Assign colors tp map
map = [1 0 0        % 1 = red
       1 0.5 0      % 2 = orange
       1 1 0];      % 3 = yellow
colormap(map)
color = areas(:,3);

patch(subAx1,x1,y,color, 'FaceAlpha',0.3, 'EdgeColor','none');
patch(subAx2,x2,y,color, 'FaceAlpha',0.3, 'EdgeColor','none');
patch(subAx3,x3,y,color, 'FaceAlpha',0.3, 'EdgeColor','none');

% Set axes limits
subAx1.XLim = xlimit1;
subAx2.XLim = xlimit2;
subAx3.XLim = xlimit3;
subAx1.YLim = [0 80];
subAx2.YLim = [0 80];
subAx3.YLim = [0 80];

Answer 1

[Stephen23]

Set the caxis limits:

https://www.mathworks.com/help/matlab/ref/caxis.html

A simple working example:

>> map = [1,0,0;1,0.5,0;1,1,0]; % red;orange;yellow
>> colormap(map)
>> patch([0,1,2,0],[0,2,0,0],3) % 3 -> should be yellow
>> saveas(gcf,'Before.png')
>> caxis([1,3])                 % set the color limits
>> saveas(gcf,'After.png')

Before:

After:

[Michael Steinbuechler]

Hello Stephen,

Thanks for the fast reply.

Okay this definitly makes sense, but it doesnt seem to work with 'patch'. Thats what I get as a result:

[Michael Steinbuechler]

Okay I found the problem. Seems like the caxis command doesnt like subplots if it doesnt get a handle.

Thats what the solution in my case looks like:

subAx1.CLimMode = 'manual';
subAx2.CLimMode = 'manual';
subAx3.CLimMode = 'manual';

subAx1.CLim = [1,3];
subAx2.CLim = [1,3];
subAx3.CLim = [1,3];

Thank you very much!!!

[Stephen23]

According to the caxis documentation this should also work:

caxis(subAx1,[1,3])
caxis(subAx2,[1,3])
caxis(subAx3,[1,3])