How can I somehow highlight (with a specific color, for example) some cells in a heatmap, like only those whose values meet a condition, such as > 200?

heatmap(1:5,1:5,randi(250,[5 5]));

Answer 1

[Sandeep Mishra]

Hello Laura,

I understand that you want to create a heatmap for some range of values and want to highlight some specific cells with values greater than the threshold 200.

In MATLAB, “heatmap" provides you with the functionality to create a heatmap chart with specified values and add colors to them based on those values.

To customize the color of the cells, you can use the “Colormap” parameter and create a custom colormap.

Here's one way to create a custom colormap with a threshold and maxValue value.

% Setting up threshold and maxValue 
threshold = 200;
maxVal = 250;

% Custom color map
cmap = [];

% Generating default heatmap till threshold
for i=1:threshold+1
    cmap = [cmap; 1 - 0.0035*i , 1 - 0.0020*i,  1-0.0009*i];
end

% Adding different color (red) for values > threshold
cmap = [cmap; repmat([1 0 0], maxVal-threshold-1, 1)];

% plots heatmap with cmap as colormap
figure();
h=heatmap(1:5, 1:5, randi(maxVal,[5 5]));
h.Colormap = cmap;

% set the clim:
clim([0 maxVal]);

You can refer to the below documentation to learn more about "Colormap" in MATLAB.

Heatmap chart appearance and behavior - MATLAB - MathWorks India

[Laura Gianolio]

Hello Sandeep, that's just what I meant! Thanks a bunch!!!