Warning "Ignoring extra legend entries"

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

So I do not know why it gives me that .Can someone explain, and any methods to solve it ?

Thanks in advance,

Khang

Answer 1

[Alex Mcaulley]

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.

[Khang Nguyen]

Oh i didnt notice that. Thank you so much for helping

[Alex McCracken]

I did a similar thing, I called legend() before I had input all of my variables, so just put legend() at the end of the figure's code helps

[Shreyas Taware]

It can be avoided if you type 'hold on' below the legend in each loop

Answer 2

[neelu pareek]

thanks a lot

Answer 3

[Pierre MORETTO]

What to do if we want a specific legend per figure ?

Answer 4

[Cameron J Reimer]

thanks

[Shreen El-Sapa]

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.