MATLAB: How to modify the X and Y axis tick labels for a Heatmap chart

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How can I modify the X and Y axis tick labels for a 'Heatmap' chart?

My data is too dense (100 ticks on each axis) and tick labels overlap each other if all of them are plotted.

For example, how can I only display every '5th' tick label, instead of all of them?

Best Answer

I understand that you are trying to change the displayed tick labels on the X and Y axis of a 'Heatmap'.

For this you need to set the 'XDisplayLabels' property of the heatmap object.

The following link provides more information on this:

   <https://www.mathworks.com/help/matlab/ref/matlab.graphics.chart.heatmapchart-properties.html#d117e582387>

I created an example MATLAB script to demonstrate how this may be done, as follows:

% Create a random 2-D matrix and make a heatmap
A = randi(100,100);
h = heatmap(A);

Create custom X tick labels such that every tick label is blank (i.e., " ") except ticks which are divisible by 5 (i.e., 5, 10, 15, ...)

XLabels = 1:100;
% Convert each number in the array into a string
CustomXLabels = string(XLabels);
% Replace all but the fifth elements by spaces
CustomXLabels(mod(XLabels,5) ~= 0) = " ";
% Set the 'XDisplayLabels' property of the heatmap 
% object 'h' to the custom x-axis tick labels
h.XDisplayLabels = CustomXLabels;

In the above example we create a random (100 X 100) matrix of numbers 'A' and use it to create a Heatmap 'h':

Assuming that we only want to display every 5th tick label on the X-axis of the Heatmap, I create a (1 X 100) array of strings 'CustomXLabels'.

Every element of 'CustomXLabels' is an white space (i.e., ' ' ) except for the ones that are divisible by 5 (these elements will be strings like: '5', '10', '15', ...., '100').

Next, we set the 'XDisplayLabels' property of the Heatmap object 'h' with the custom labels array 'CustomXLabels', which sets the X-Axis tick labels as per our requirements:

Related Solutions

MATLAB: Set the Location of R-axis Labels using ‘polar’ in MATLAB R2016a

Moving the R-axis with 'polarplot' The 'polarplot' function was introduced in MATLAB R2016a as a replacement for the 'polar' function, which makes it easier to customize polar plots.

See the documentation linked below, which outlines the properties of 'polaraxes' for more information:

https://www.mathworks.com/help/releases/R2016a/matlab/ref/polaraxes-properties.html

The 'RAxisLocation' property can be used to set the location of the R-axis labels in degrees:

% Create a polar plot.
pp = polarplot(sin(0:0.01:10*pi));
% Get a handle to the polar plot axes.
ax = gca;
% Set the location of the R-axis labels in degrees.
degrees = 300;
ax.RAxisLocation = degrees;

If you are unable to use the 'polarplot' function, you can follow the workarounds below to hide or move the R-axis labels using the 'polar' function.

Hiding the R-axis with 'polar' 1.) To hide the R-axis labels, first locate all of the 'Text' objects in the graphics object hierarchy using the 'findall' command. Then, filter the results using the 'HorizontalAlignment' property of the 'Text' objects.

PLEASE NOTE: This filtering method relies on the default value being set to 'left' for the 'HorizontalAlignment' property of the 'Text' objects created by the 'polar' command.

% Taken from 'doc polar' example:

% http://www.mathworks.com/help/matlab/ref/polar.html

theta = 0:0.01:2*pi;
rho = sin(2*theta).*cos(2*theta);
f = figure;
polar(theta,rho,'--r');
% Extract all of the 'Text' objects from the polar plot.

ax = findall(f.Children, 'Type', 'Axes');
% Filter the 'Text' objects by the 'HorizontalAlignment' property.

% PLEASE NOTE: This may not generalize to other versions of MATLAB

% where the default 'HorizontalAlignment' value for R-axis labels is not

% set to 'left'.

labels = findall(ax, 'Type', 'Text', 'HorizontalAlignment', 'left');
% Hide all the R-axis labels.
[labels.Visible] = deal('off');

Moving the R-Axis with 'polar' 2.) To move the R-axis labels, first locate the corresponding 'Text' objects in the graphics object hierarchy, as described above. Then, iterate over the appropriate set of 'Text' objects, and update the 'Position' property of each object.

The code below provides a simple method of setting the 'Position' property of each 'Text' object in degrees on the polar plot. You can modify the value of the 'degrees' variable to choose where you want to place the R-axis labels on the polar plot.

% Taken from 'doc polar' example:
% http://www.mathworks.com/help/matlab/ref/polar.html
theta = 0:0.01:2*pi;
rho = sin(2*theta).*cos(2*theta);
f = figure;
polar(theta,rho,'--r');
% Extract all of the 'Text' objects from the polar plot.
ax = findall(f.Children, 'Type', 'Axes');
% Filter the 'Text' objects by the 'HorizontalAlignment' property.
% PLEASE NOTE: This may not generalize to other versions of MATLAB
% where the default 'HorizontalAlignment' value for R-axis labels is not
% set to 'left'.
labels = findall(ax, 'Type', 'Text', 'HorizontalAlignment', 'left');
% Set the degrees of the R-axis Labels.
degrees = 300;
% Update the position of each R-axis label.
for label = labels'
    currentX = label.Position(1);
    currentY = label.Position(2);
    radius = sqrt(currentX^2 + currentY^2);
    newX = cos(degtorad(degrees)) * radius;
    newY = sin(degtorad(degrees)) * radius;
    label.Position = [newX, newY];
end

MATLAB: How to modify the datetime ticks used in heatmaps

The below code helps

CustomXLabels = string(x_time);
% Replace all but the tenth elements by spaces
CustomXLabels(mod(minute(x_time),10) ~= 0) = " ";
% Set the 'XDisplayLabels' property of the heatmap object 'h1' to the custom x-axis tick labels
h1.XDisplayLabels = CustomXLabels;
 
axs = struct(gca);
cb = axs.Colorbar;
cb.TickLabels = {'foo 0.1','foo 0.2','...'};

Best Answer

Related Solutions

MATLAB: Set the Location of R-axis Labels using ‘polar’ in MATLAB R2016a

MATLAB: How to modify the datetime ticks used in heatmaps

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