Controlling the size of legend markers separately from the font size of legend labels

I need to control the markers in my legend separately from the font size of the legends' labels. Inspired by this previous answer, I used this code, in Matlab 2016a:

    x = 1:10;
    plot(x, 1*x, 'o')
    hold on
    plot(x, 2*x, 's')
    h_legend = legend({'one','two'});
    objhl = findobj(h_legend, 'type', 'line'); % objects of legend of type patch
    set(objhl, 'Markersize', 99); % set marker size as desired

Funnily enough, this solution worked for me for a few plots. However, after a while, now whatever I type in place of the 99, makes no difference. If I change the 'line' into 'patch, that also makes no difference. The problem I guess comes from the fact that objhl is actually empty:

    >> objhl = findobj(h_legend, 'type', 'patch')
    objhl = 
      0x0 empty GraphicsPlaceholder array.

Any thoughts? Many thanks!

Answer 1

[Subhadeep Koley]

A new MATLAB graphics system is introduced from MATLAB R2014b onwards. Your code will work for the older system I guess.

Use the code below if you are using MATLAB R2014b or later.

clc; close all;
x = 1:10;
plot(x, 1*x, 'o');
hold on;
plot(x, 2*x, 's');
[~, objh] = legend({'one','two'}); % Instead of "h_legend" use "[~, objh]"
objhl = findobj(objh, 'type', 'line');
set(objhl, 'Markersize', 15);

[z8080]

Thank you Subhadeep!

[Adam Danz]

Note that since r2018b only the first output of the legend function is documented. Archived documentation for the legend function from r2016a to r2018a suggests avoiding the use of the outputs other than the first output:

Note: This syntax is not recommended and creates a legend that does not support all graphics features. Use the l = legend(__) syntax to return the legend object and set Legend Properties instead.

For example, if the first and second outputs to legend() are both included, it interferes with the ability to change the fontsize of the legend text.

[Afiq Azaibi]

Starting in R2024b, calling legend with multiple outputs will throw a warning. It will continue to function as it has previously.

Answer 2

[Adam Danz]

This solution avoids the use of undocumented legend outputs that have caused problems in the past (example 1, example 2).

% Plot data
x = 1:10;
plot(x, 1*x, 'bo');
hold on;
plot(x, 2*x, 'rs');

% Create customizable objects that won't appear on the axes
% but will appear in the legend
h(1) = plot(nan, nan, 'bo', 'MarkerSize', 15, 'DisplayName', 'one');
h(2) = plot(nan, nan, 'rs', 'MarkerSize', 15, 'DisplayName', 'two');
legend(h)

[Subhadeep Koley]

@ Adam Danz Nice solution!

[Yami]

The code above changed the marker's color. So I have used this code which is almost the same:

Matlab R2019b

f12=figure('Name', 'Plot_name', 'visible','off');
hold on;
plot(data(1,:), data(74,:), 'linestyle','none','marker','o', 'MarkerSize', 0.5, 'color', '#000080');
plot(data(1,:), data(75,:), 'linestyle','none','marker','o', 'MarkerSize', 0.5, 'color', '#000000');
plot(data(1,:), data(76,:), 'linestyle','none','marker','o', 'MarkerSize', 0.5, 'color', '#6897bb');
xlabel('Time in s');
ylabel('Est. M. F.');
axis([-inf inf 0 1.1]);
grid on;
box on;
% legend
h(1)=plot(nan, nan, 'o', 'MarkerSize', 5, 'DisplayName', 'Est. H20', 'color', '#000080');
h(2)=plot(nan, nan, 'o', 'MarkerSize', 5, 'DisplayName', 'Est. H2', 'color', '#000000');
h(3)=plot(nan, nan, 'o', 'MarkerSize', 5, 'DisplayName', 'Est. N2', 'color', '#6897bb');
legend(h, 'Location','east');

[Adam Danz]

> The code above changed the marker's color.

Are you refering to the code from my answer? That only changes marker size, not marker color.

[Francesco Bernardini]

Amazing! Thanks a lot