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Warning "Ignoring extra legend entries"

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Hi everyone,
so this is my code, sorry if it distracts you, please let me know.Just put the code so that everyone knows excactly what is my question. Please just scroll down to read my questions, and use the code for solving it.
%% variable declaration
colours = 'rbk';
%% Solve ODEs using Euler's method
figure(4) %figure 4
%Input
y0 = 1;
z0 = 1;
u = 1;
tspan = [0 30];
%two first order ODE
dydt = @(t,z) z;
dzdt = @(y,z) u*(1-y^2)*z - y;
% solving ODE for each h value
%Creating vector h
h = [0.25,0.125,0.0625];
%forming a matrice of cells since each variables has different size
t_e=cell(1,length(h));
y_e=cell(1,length(h));
z_e=cell(1,length(h));
%Solving ODE for each h value
for i = 1:length(h)
[t_e{i},y_e{i},z_e{i}] = euler2(dydt,dzdt,tspan,y0,z0,h(i));
end
%plotting
for i = 1:length(h)
subplot(2,1,1)
hold on
plot(t_e{1,i},y_e{i},colours(i));
xlabel('t')
ylabel('y')
title('y against t')
legend('step size = 0.25','step size = 0.125','step size = 0.0625','Location','nw')
subplot(2,1,2)
plot(t_e{1,i},dydt(t_e{1,i},z_e{1,i}),colours(i));
hold on
xlabel('t')
ylabel('dydt')
title('dydt against x')
legend('step size = 0.25','step size = 0.125','step size = 0.0625','Location','nw')
end
%print the method that increase the accuracy
fprintf('The accuracy of the solutions can be improved by \nreducing the step size of h, as it can be seen in the graph')
%function file
if ~(tspan(2)>tspan(1))
error('upper limit must be greater than lower')
end
% Create all independent values, t
%use tspan to create a vector with spacing = h;
t = [tspan(1):h:tspan(2)]';
n = length(t);
if t(end) < tspan(2)
t(n+1) = tspan(2);
n = n+1;
end
% add extra t-value if needed
%check if final t-value can be achieved using the current h
%if not, add a new t-value to the end of t
% Implement Euler's method
%use a for loop
%pre allocate the solution vector
%y = zeros(1,n)
%z = zeros(1,n)
%y(1) = y0
%z(1) = z0
y = y0*ones(n,1);
z = z0*ones(n,1); % 1 line
for i = 1:n-1 %stop at n-1 because dont need to calculate the deriative for final interation
%singeline for euler's method
z(i+1) = z(i) + h*dzdt(y(i),z(i));
y(i+1) = y(i) + h*z(i);
end
%%%% Question
When i run this code, it gives me the error
61281388_425247231389910_3749113343936299008_n.png
So I do not know why it gives me that .Can someone explain, and any methods to solve it ?
Thanks in advance,
Khang

Accepted Answer

Alex Mcaulley
Alex Mcaulley on 23 May 2019
You are calling legend in each iteration of the loop. In the first 2 iterations your plots have less than 3 lines and you are calling legend with three labels, then the warning is generated.
To supress this warning just call legend out of the loop.
  3 Comments
Shreyas Taware
Shreyas Taware on 11 Mar 2021
It can be avoided if you type 'hold on' below the legend in each loop

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More Answers (3)


Pierre MORETTO
Pierre MORETTO on 5 Dec 2020
What to do if we want a specific legend per figure ?

Cameron J Reimer
Cameron J Reimer on 1 Mar 2021
thanks
  1 Comment
Shreen El-Sapa
Shreen El-Sapa on 2 Apr 2021
Can you help me?
%========================================================
plot(kappa,drag1,'-K',kappa,drag2,'--K');
%plot(kappaappa,kappa1,'-kappa',kappaappa,kappa2,'--kappa',kappaappa,kappa3,'-.kappa',kappaappa,kappa4,':kappa',kappaappa,kappa5,'-kappa',kappaappa,kappa6,'--kappa',kappaappa,kappa7,'-.kappa',kappaappa,kappa8,':kappa');
ylabel('$F/F_{0}$','Interpreter','latex','FontSize',12,'FontName','TiemsNewRoman','FontWeight','Normal')
xlabel('$\kappa$','Interpreter','latex','FontSize',12,'FontName','TiemsNewRoman','FontWeight','Normal')
hold on
set(legend('\phi=1.0','\phi=10.0','NorthEast'),'FontSize',12,'FontName','TiemsNewRoman')
set(gcf,'PaperPosition',[1.5 3.25 5.5 4.5]);
axis([0 10 0 10])
then this message appears
Warning: Ignoring extra legend entries.
> In legend>process_inputs (line 587)
In legend>make_legend (line 315)
In legend (line 259)
In Force_1 (line 47)
curves donot appear also.

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