MATLAB Answers

# Single legend for plot with two axes

37 views (last 30 days)
Martin on 17 Mar 2011
Commented: Alborz Sakhaei on 4 Oct 2016
Hi,
I am trying to create a figure consisting of two axes with one plot in each one. For this figure however, I only want one legend that includes both of the plots.
An example of the plot code i would like to modify:
x = [0:0.01:5];
y1 = x.^2;
y2 = sqrt(x);
% Create figure
figure1 = figure('Units', 'pixels','Color', 'none', 'Position',[100 100 630 450]);
% Create axes 1
axes1 = axes('Parent',figure1,...
'Units', 'pixels',...
'Position',[115 85 400 305],...
'XMinorTick','on',...
'YMinorTick','on',...
'YGrid','on',...
'XTick', 0:1:5,...
'YTick' , 0:5:25, ...
'Yscale', 'linear',...
'YMinorGrid','off',...
'XColor',[0.1 0.1 0.1],...
'YColor' , [.1 .1 .1], ...
'TickDir','out',...
'TickLength',[0.02 0.02],...
'LineWidth',1,...
'FontName','Arial',...
'FontSize',12);
xlim([0 5]);
ylim([0 25]);
box('on');
hold('all');
plot(x,y1,'Parent',axes1,...
'LineWidth',2,...
'Color',[0.1 0.1 0.9],...
'DisplayName','1');
% Create axes 2
axes2 = axes('Parent',figure1,...
'Units', 'pixels',...
'Position',[115 85 400 305],...
'YTick',0:0.5:3,...
'XTick', 0:1:5,...
'YMinorTick','on',...
'Yscale', 'linear',...
'YMinorGrid','off',...
'YGrid','off',...
'YAxisLocation','right',...
'TickDir','out',...
'YColor' , [.1 .1 .1], ...
'XColor',[0.1 0.1 0.1],...
'FontName','Arial',...
'FontSize',12,...
'Color','none');
xlim([0 5]);
ylim([0 3]);
hold('all');
plot(x,y2,'Parent',axes2,...
'LineWidth',2,...
'Color',[0.9 0.1 0.1],...
'DisplayName','2');
% Create legend
legend1 = legend(axes1,'show');
legend(axes1,'boxon')
set(legend1,'Location','SouthWest','FontSize',10);
legend2 = legend(axes2,'show');
legend(axes2,'boxon')
set(legend2,'Location','SouthEast','FontSize',10);
The code plots y1 and y2 in two different axes (axes1 and axes2). I want legend1 and legend2 to be the same legend. Any ideas on how to make this happen?
##### 0 CommentsShowHide -1 older comments

Sign in to comment.

### Accepted Answer

Jan on 17 Mar 2011
You can catch the handles of the created lines to create the legend and set the legend's position manually:
subplot(1, 3, 1);
a = plot(rand(4));
subplot(1, 3, 2);
b = plot(rand(4));
Leg = legend([a; b], {'a', 'b', 'c', 'd', 'a2', 'b2', 'c2', 'd2'});
Pos = get(Leg, 'Position');
set(Leg, 'Position', [1 - Pos(3), Pos(2:4)]);

ADDED: See also: SubPlotLegend, GridLegend
##### 2 CommentsShowHide 1 older comment
Alborz Sakhaei on 4 Oct 2016
I have a figure with two axes (left and right). 2 lines on left axis and one line on right axis. I can not get all legends in one box using following code.
PS. I have read previous discussions (links below) on this topic but does not seem to work for me!
function
x = 0:0.01:10;
y11 = sin(x);
y12 = cos(x);
y2 = ones(1001,1);
figure;
ax(1) = axes('position',[0.1 0.1 0.8 0.8]);
ax(2) = axes('position',[0.1 0.1 0.8 0.8], 'yaxislocation','right','color','none');
line('parent',ax(1),'xdata',x,'ydata',y11,'color','b');
line('parent',ax(1),'xdata',x,'ydata',y12,'color','g');
line('parent',ax(2),'xdata',x,'ydata',y2,'color','r');
legend( [ax(1) ; ax(2)] , {'sin','cos','one'} )

Sign in to comment.

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!