Single legend for plot with two axes

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?

Answer 1

[Jan]

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

[Martin]

Ah, OK so this is how you do it. Just defining the legend by a vector. Thanks a lot for the answer it was really helpful.

[Alborz Sakhaei]

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!

Single legend for plot with two axes

Legend problem in a multiple axes graph

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'} )