MATLAB: Is there a command in MATLAB for creating one overall legend when I have a figure with subplots

legendMATLABoneoverallsubplot

Is there a command in MATLAB for creating one overall legend when I have a figure with subplots?

I have a figure with subplots and I would like to create one legend that refers to all of my subplots. Is there a way to do this?

Best Answer

The ability to create an overall legend for subplots is not available in MATLAB.

Currently, to work around this issue, try creating a legend using a vector of handles corresponding to the subplots. Then, move the legend manually by clicking the left mouse button on the legend and dragging it to the desired destination, or programatically using the 'Position' attribute of the legend handle. The following is an example on how to create a legend using a vector of handles and move the legend programatically.

% Construct a figure with subplots and data
subplot(2,2,1);
line1 = plot(1:10,rand(1,10),'b');
title('Axes 1');
subplot(2,2,2);
line2 = plot(1:10,rand(1,10),'g');
title('Axes 2');
subplot(2,2,3);
line3 = plot(1:10,rand(1,10),'r');
title('Axes 3');
subplot(2,2,4);
line4 = plot(1:10,rand(1,10),'y');
title('Axes 4');
% Construct a Legend with the data from the sub-plots
hL = legend([line1,line2,line3,line4],{'Data Axes 1','Data Axes 2','Data Axes 3','Data Axes 4'});
% Programatically move the Legend
newPosition = [0.4 0.4 0.2 0.2];
newUnits = 'normalized';
set(hL,'Position', newPosition,'Units', newUnits);

-Note 1: This will create the legend in the axes which corresponds to the first handle passed into LEGEND. In this case, the legend will appear in the bottom subplot since that is the axes in which "h2" is plotted in.

-Note 2: The legend is a wrapper for axes and is thus parented to the figure. You can use its handle to reposition it within the figure.

Related Solutions

MATLAB: Legend title won’t display correctly.

OK, I see I overlooked the needed (albeit hidden) property that needed most to get where you want to go...

Try exploring from this point:

figure
hL=plot(0,0,  0,0,  0,0);             % three dummy lines to legend something
axis off                              % don't show the axis
hLg=legend({'Data Axes 1','Data Axes 2','Data Axes 3'},'FontSize',24);  % so create the base legend object
hLgT=title(hLg, "My title, and it can be long");                        % title, save handle to mung o
hLgAx=hLg.Axes;                        % retrieve the axes underlying the legend (there is still one there)
hLgLn=findobj(hLgAx,'Type','Line');    % and the handles for the lines on that axes
set(hLgLn,'LineWidth',2)               % set their width property

Thanks to Yair Altman's tool for finding the hidden properties underneath the legend...and, of course, since is all undocumented, who know how long will be before TMW changes something else altho wouldn't expect the axes to go away.

This produces a full-size figure, of course, I didn't mess with the position/size, etc., but everything should work on that axes as expected; just more complicated to get access than needs must be. Why TMW is so bent on making things more rather than less difficult is hard to comprehend.

ADDENDUM

https://www.mathworks.com/matlabcentral/fileexchange/32934-getundoc-get-undocumented-object-properties

ADDENDUM 2:

There's another hidden property PlotChildren that returns the line handles directly without having to go "handle diving" under the axis altho they're in the opposite order in the two arrays for some reason.

> hLgLn=findobj(hLgAx,'Type','Line')
hLgLn = 
  3×1 Line array:
  Line    (Data Axes 3)
  Line    (Data Axes 2)
  Line    (Data Axes 1)
>> hLg.PlotChildren
ans = 
  3×1 Line array:
  Line    (Data Axes 1)
  Line    (Data Axes 2)
  Line    (Data Axes 3)
>> all(flip(hLgLn)==hLg.PlotChildren)
ans =
  logical
   1
>>

MATLAB: Multiple plots with same Legend

The issue here is that each legend needs to be associated with an axis. There is no built-in way to create an "overall legend". But it is perfectly fine to use a legend associated with a subplot as an overall legend. You will have to play with the legend's position to achieve the desired look.

The easiest way to do it is manually, by dragging the legend inside the figure.

It is a bit more involved programmatically. Here is an example:

subplot(2, 2, 1)
A = rand(10, 3);
plot(A, '-o')
hold on
b = rand(10, 1);
plot(b, '-k', 'LineWidth', 3)
subplot(2, 2, 2)
A = rand(10, 3);
plot(A, '-o')
hold on
b = rand(10, 1);
plot(b, '-k', 'LineWidth', 3)
subplot(2, 2, 3)
A = rand(10, 3);
plot(A, '-o')
hold on
b = rand(10, 1);
plot(b, '-k', 'LineWidth', 3)
subplot(2, 2, 4)
A = rand(10, 3);
plot(A, '-o', 'DisplayName', 'Data')
hold on
b = rand(10, 1);
plot(b, '-k', 'LineWidth', 4, 'DisplayName', 'Trend')
% add a bit space to the figure
fig = gcf;
fig.Position(3) = fig.Position(3) + 250;
% add legend
Lgnd = legend('show');
Lgnd.Position(1) = 0.01;
Lgnd.Position(2) = 0.4;

Best Answer

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MATLAB: Legend title won’t display correctly.

MATLAB: Multiple plots with same Legend

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