MATLAB: Edit colorbar of heatmap (string)

colorbarcolormapdesignheatmapMATLABplotplottingyticklabel

Hi,

Is it possible to edit the colorbar of a heatmap such that it looks like the following image (rapidly created with paint 😉 )

So the values aren't numeric but strings.

Thanks for help!

Best Answer

This can't be done with heatmap() (see comments under the question).

If you're using a different function that allows access to the colobar, it's fairly straightforward. Here's a demo.

% Create demo
C = rand(3,4)/10; 
imagesc(C)
cbh = colorbar(); 
% set color range
caxis([0,.1])
% set ticks 
set(cbh, 'YTick', [0.001, 0.01, 0.05, .1], ...
    'YTickLabel', {'p=0.001', 'p=0.01', 'p=0.05', 'p=.1'})

Related Solutions

MATLAB: How to move a colorbar when using heat maps? (2017a)

That does not appear to be possible.

heatmap() turns out to create a sort of axis object, and colorbar notices that its parent is a heatmap and refuses to do some things.

If you do

ax = gca;     %then ax becomes the handle to the heatmap
axs = struct(ax);   %and ignore the warning
cb = axs.Colorbar;    %now you have a handle to the colorbar object

However, if you try to set cb.Position then that will fail: the colorbar is being controlled by a layout manager which will promptly get confused and error out.

MATLAB: How to remove the Range from colorbar in HeatMap

Heatmaps are notoriously difficult to customize outside of the HeatmapChart Properties. The only property that I'm aware of that affects the heapmap colorbar is the ColorbarVisible property that just turns the colorbar on/off and resizes the heatmap accordingly.

One alternative is to use imagesc() instead which gives you full access to the colorbar and many other properties.

If you'd like to stick with a heatmap, here's a workaround that puts a customizable colorbar on top of the existing heatmap colorbar.

% Create the heatmap with a heatmap-colorbar
fh = figure();         % We'll use the figure handle.
clf()
data = randi(3,8,8)-1; 
data(logical(eye(8))) = NaN; 
hm = heatmap(data);    % We'll use the heatmap output object.
colormap([1 0 0; 1 1 0; 0 1 0])
% Put an axis over top of the heatmap
% The axis will not be visible but will cover all area 
% to the right of the heatmap. 
hmp = hm.Position; 
cbax = axes('Position',[sum(hmp([1,3])), 0, 1-sum(hmp([1,3])), 1],...
    'XTick',[], 'YTick', [], 'Color',fh.Color);
cbax.XAxis.Visible = 'off';
cbax.YAxis.Visible = 'off';
% Set the new axis color map to match the 
% heatmap's colormap
cbax.Colormap = hm.Colormap; 
% Add a colorbar the same vertical position as the heatmap
cbh = colorbar(cbax,'Position',[.90, hmp(2), .03, hmp(4)]); 
% Set the limits to 0:1 and set the ticks so that they 
% are in the center of each bar
cbh.Limits = [0,1]; 
nColors = size(hm.Colormap,1); 
cbh.Ticks = (1/nColors : 1/nColors : 1) - 1/nColors/2; 
% Set the new labels for each tick
cbh.TickLabels = 0:nColors-1; 
% Set the colorbar fontsize to the same value as heatmap fontsize
cbh.FontSize = hm.FontSize;

Note that the NaN values are no longer represented in the new colorbar.

Best Answer

Related Solutions

MATLAB: How to move a colorbar when using heat maps? (2017a)

MATLAB: How to remove the Range from colorbar in HeatMap

Related Question