MATLAB: Colorbar with diamond-shape blocks

colorbarcustom legendgridplotpseudo legendshape

Hello,

I want to plot a colorbar with customized shapes. When I execute the colorbar command, I get the following colorbar in which each block is rectangular-shaped.

However, I want to plot the colorbar in which each block has a diamond shape as shown in the following eample:

Screen Shot 2020-01-24 at 2.34.23 PM.png

Is it possible to customize the shape of the grid boxes like this?

Any help will be greatly appreciated.

Regards,

Best Answer

Here are two methods to create a custom legend.

Method 1: Plot dummy variables that only appear in the legend.

plot(nan,nan,'d') will produce a point in the legend but won't appear in the axes.

clf()                
axes()                                    % main axis
hold on                                   % important!
nMarkers = 10;                            % number of markers/colors

labels = 5:5:50;                          % legend labels
colors = jet(nMarkers);                   % Color of each marker (by row)

sh = arrayfun(@(i)scatter(nan,nan,50,colors(i,:),...    % plot invisible markers
    'd','filled','DisplayName',num2str(labels(i))),...
    1:nMarkers);
legend(sh)                                % Specify invisible marker handles

If you'd rather use plot() instead of scatter(),

sh = arrayfun(@(i)plot(nan,nan,'d','Color','none',...
    'MarkerFaceColor',colors(i,:),'DisplayName',...
    num2str(labels(i))),1:nMarkers);

Method 2: Create a pseudo-legend on a separate axes

Produce a 2nd axes and use text() to label points.

clf()
axes('Position',[.1 .1 .7 .7])            % main axes
cbax = axes('position',[.83 .1 .05 .7]);  % color legend axes
nMarkers = 10;                            % number of markers/colors
y = linspace(0.4,1,nMarkers);             % y value of each marker
x = zeros(size(y));                       % x value of each marker
labels = strsplit(strtrim(num2str(5:5:50)));  % "legend" strings
colors = jet(nMarkers);                   % Color of each marker (by row)
scatter(cbax,x,y,50,colors,'d','filled')  % plot the colored diamonds
ylim(cbax,[0,1])                          % Scale the y axis for spacing
text(cbax,x+.4,y,labels,'FontSize',8)     % Add the "legend" strings
axis(cbax,'off')                          % Turn off the legend axis

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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

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