# legend with multiple axes using yyaxis

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nathan blanc on 2 Jan 2021
Commented: Star Strider on 2 Jan 2021
I am creating a plot with two different y axes. the curves are added alternately. for example:
yyaxis left
plot(A)
yyaxis right
plot(B)
yyaxis left
plot(C)
yyaxis right
plot(D)
My problem is that when I add a legend to the plot, the order of the curves is not the order in which they were created. instead, they are ordered first by the left axis
and then by the right axis. meaning if i write down "legend(A,B,C,D)" the legend entry B will correspond with the curve C and vice-versa. is there a way to fix this? The actual case there are more than 4 curves, and the number changes every time, so manual changing is not possible. many thanks in advance
Nathan

Star Strider on 2 Jan 2021
Edited: Star Strider on 2 Jan 2021
Try this:
A = rand(1,10);
B = rand(1,15);
C = rand(1,20);
D = rand(1,30);
figure
hold on
yyaxis left
ha = plot(A);
yyaxis right
hb = plot(B);
yyaxis left
hc = plot(C);
yyaxis right
hd = plot(D);
hold off
legend([ha,hb,hc,hd], 'A','B','C','D')
Alternatively:
figure
yyaxis left
ha = plot(A);
hold on
hc = plot(C);
hold off
yyaxis right
hb = plot(B);
hold on
hd = plot(D);
hold off
legend([ha,hb,hc,hd], 'A','B','C','D')
Using hold is the only way to do what you want. This cannot be used with your posted code, because without the hold function, the second calls to yyaxis left and yyaxis right calls eliminate the handles to the previously plotted curves.
EDIT — (2 Jan 2021 at 17:41)
.
##### 2 CommentsShowHide 1 older comment
Star Strider on 2 Jan 2021
As always, my pleasure!
The hold function permits subsequent plots on the same axes, and that is necessary here. (I thought that I already posted a link to that function, however I now realise that did not, and have now corrected that. My apologies for the oversight.)

R2020b

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