MATLAB: Legend for plotyy causes axes problem

axislegendplotyy

Hello!

Can anyone help me?

The legend in my plot generated by plotyy causes a displacement of one y-axis.

Does anyone knows a solution? Thanks

 x = 1:100;
 y1= randn(1,length(x));
 y2= randn(1,length(x));
 y3= randn(1,length(x));
 y4= randn(1,length(x));
 % plot1
    [hA,h1,h2] = plotyy(x,y1,x,y2);
    hold on
 % plot2
    [hB,h3,h4] = plotyy(x,y3,x,y4);
 hold off
 legend([h1,h2,h3,h4],'a','b','c','d','location','northoutside','orientation','horizontal')
 refresh

Best Answer

There are multiple axes created by plotyy and hold operates on only one at a time (and, disappointingly, won't accept a vector of multiple handles). Then, on top of that, when you use plotyy a second time you end up creating yet a third axis...

After executing your plotting calls--

>> [hA; hB]  % look at axes handles...
ans =
173.0382  175.0382
173.0382  180.0382
>>

Note the LH axes was plotted into with the second call but a second RH axis was created. So, now you've got three to try to synchronize if you do that. So, "don't DO that!!!" :)

Instead,

>> [hA,h1,h2] = plotyy(x,y1,x,y2);  % first call to create the two axes
>> set(hA,'nextplot','add')         % "hold on" for multiple axes
>> h3 = plot(hA(1),x,y3);           % add to the LH axis
>> h4 = plot(hA(2),x,y4);           % and to the RH one as well
>> legend([h1,h2,h3,h4],'a','b','c','d','location','northoutside','orientation','horizontal')
>>

Now axes will be in synch and both reduced to place the legend as desired.

Related Solutions

MATLAB: Legend for yyaxis at two different locations

The second call to legend() is replacing the first legend (you can only have 1 legend).

I reworked your code to use yyaxis instead of plotyy.

Solution 1: use 1 legend

This solution puts all handles into the same legend. See inline comments for details.

n=-180:180;
x=(pi/180).*n;
y=sin(x);
y2=sin(x).*cos(x);
y3=cos(x);
% Plot on left axis

yyaxis left
h1 = plot(n,y, '-k', 'LineWidth', 1, 'DisplayName', 'h1'); 
set(gca, 'YColor', 'k') % set y axis color to same as line color



hold on
h3=line(n,y3,'Color','r','LineWidth',2, 'DisplayName', 'h3');
% Plot on right axis

yyaxis right
h2 = plot(n,y2, '-b', 'LineWidth', 1.5, 'DisplayName', 'h2'); 
set(gca, 'YColor', 'b') % set y axis color to same as line color

Solution 2: kludge in a 2nd legend

Since you can only have 1 legend per axis, this solution produces a second invisible axis and copies the h2 object to the invisible axis so that it can have its own legend. See inline comments for details.

n=-180:180;
x=(pi/180).*n;
y=sin(x);
y2=sin(x).*cos(x);
y3=cos(x);
% Plot on left axis
yyaxis left
h1 = plot(n,y, '-k', 'LineWidth', 1, 'DisplayName', 'h1'); 
set(gca, 'YColor', 'k') % set y axis color to same as line color
hold on
h3=line(n,y3,'Color','r','LineWidth',2, 'DisplayName', 'h3');
% Plot on right axis
yyaxis right
h2 = plot(n,y2, '-b', 'LineWidth', 1.5, 'DisplayName', 'h2'); 
set(gca, 'YColor', 'b') % set y axis color to same as line color
% Produce left-axis legend
legend([h1,h3], 'Location', 'NorthWest')
% Create invisible axis in the same position as the current axes
ax = gca(); % Handle to the main axes
axisCopy = axes('Position', ax.Position, 'Visible', 'off');
% Copy objects to second axes
hCopy = copyobj(h2, axisCopy); 
% Replace all x values with NaN so the line doesn't appear
hCopy.XData = nan(size(hCopy.XData)); 
% Create right axis legend
legend(hCopy, 'Location', 'NorthEast')

MATLAB: How to change the color of a plot with two y-axes on the same graph in Matlab

x = 0:0.01:20;
y1 = sin(x);
y2 = x;
figure % new figure

plotyy(x,y1,x,y2)
[hAx,hLine1,hLine2] = plotyy(x,y1,x,y2);
set(hAx(1),'ycolor','r');  % Change the color accordingly

set(hAx(2),'ycolor','c');  % Change the color accordingly
xlabel('Time (\musec)')
ylabel(hAx(1),'Slow Decay') ;
ylabel(hAx(2),'Fast Decay') ;

x = 0:0.01:20;
y1 = sin(x);
y2 = x;
figure % new figure
plotyy(x,y1,x,y2)
[hAx,hLine1,hLine2] = plotyy(x,y1,x,y2);
set(hAx,{'ycolor'},{'r';'c'});
%..........x or y axex color, if x, use xcolor and change the colors accordingly
xlabel('Time (\musec)')
ylabel(hAx(1),'Slow Decay') 
ylabel(hAx(2),'Fast Decay')

Best Answer

Related Solutions

MATLAB: Legend for yyaxis at two different locations

MATLAB: How to change the color of a plot with two y-axes on the same graph in Matlab

Related Question