Manual division of the colorbar

Hello everyone,

I'm trying to have a colorbar with only the value 0 will be in a specific grey. all values above, even slightly, will be in a different color, and I want the colorbar to be descrete, meaning 5-10 will have certain color, and not every number will have a different color.

This is the colorbar I have:

And this is the colorbar I want (but prettier ;) ):

Is there any way to do that?

Thank you in advance.

[Rik]

I don't know how to do it through this UI, but it isn't hard to define a colormap in code. Have you tried that? It should be possible to extract what you have and simply remove one element.

[Eylon Vakrat]

I did try to do that, however, I was unsuccsesful.

[Rik]

What exactly did you try? I don't recognize the interface, so I don't know how to most easily extract the colormap from this point.

[Stephen23]

"I don't recognize the interface..."

It is a recent version of the inbuilt COLORMAPEDITOR()

Answer 1

[Nehemiae]

Hello,

It is possible to create a colormap with colours specified over ranges of inputs, and then input values within the specified ranges are scaled accordingly. This is shown in the case 1 of the code below. Based on the resolution chosen – a small set of values around 0, will be grey. In the second case, based on the kind of plot required (here heatmap was used), it is possible to set the input values with 0 to NaN, and display them in a separate colour using the “MissingDataColor” property.

colors = [255 0 0; 255 140 0; 255 255 0; 0 255 0; 0 0 255; 75 0 130] / 255; % Colors to be used in the colormap 

c_levels = [0 5 10 15 20 25 30]; % Levels at which the color changes: 

level_res = 0.001; % Resolution of each level 
n_colors = round(diff(c_levels) / level_res); % Total number of colors in the map 

% Create the colormap 
cmap = []; 
for i = 1 : numel(n_colors) 
    cmap = [cmap; repmat(colors(i, :), n_colors(i), 1)]; 
end 

% Case 1: Grey color over a range 
cmap1 = cmap; 
cmap1(1, :) = [105 105 105] / 255; % Change the color of value 0 to required grey 

data = [0; 0.000000001; 0.001; 0.01; 0.1; 1; 5; 10; 15; 20; 25]; 

figure; 
h = heatmap(data); 
h.Colormap = cmap1; 
caxis([0 30]); 

% Case 2: Only zero set to grey in heatmap 
cmap2 = cmap; 

data(data == 0) = NaN; 

figure; 
h = heatmap(data); 
h.Colormap = cmap2; 
h.MissingDataColor = [105 105 105] / 255; 
caxis([0 30]);

The documentation on HeatmapChart properties (https://www.mathworks.com/help/matlab/ref/matlab.graphics.chart.heatmapchart-properties.html) can be helpful in understanding the above code.