Problems with the legend function.

I'm in truble with the legend function.

I have a function plot_f.m which plots a function with its legend.

function plot_f

M=1000;
x=linspace(-11,15,M);
y=linspace(-7,11,M);

f1=0.1.*x.^3+12.*sin(x)+1.7.^(-x)-x.^2;
f2=0.1.*y.^3+12.*sin(y)+1.7.^(-y)-y.^2;
f=@(x)(0.1.*x.^3+12.*sin(x)+1.7.^(-x)-x.^2);

p1=plot(x,f1,'Color','b'); hold on;
p2=plot(y,f2,'Color',[0,1,0],'LineWidth',3);
p3=plot(-7.000,f(-7.000),'sq','MarkerSize',8,'MarkerFaceColor',[1 0 0]);
   plot(-1.850,f(-1.850),'sq','MarkerSize',8,'MarkerFaceColor',[1 0 0]);
   plot( 4.931,f( 4.931),'sq','MarkerSize',8,'MarkerFaceColor',[1 0 0]);
   plot(10.007,f(10.007),'sq','MarkerSize',8,'MarkerFaceColor',[1 0 0]);

xlim([-15 15])
ylim([-70 80])
ax = gca;
ax.XAxisLocation = 'origin';
ax.YAxisLocation = 'origin';
legend([p1,p2,p3],{'Función', 'Función en [-7,11]', 'Óptimos locales'})
box off
hold on
end

In the main program I make a call to this function and I want to add more information to the legend.

% Ejercicio 2:
% Uso de Matlab para la minimización de una funcion real
% con varios puntos de minimo local :
%               
% min: f(x)=0.1.*x.^3+12.*sin(x)+1.7.^(-x)-x.^2
% restricciones: ninguna
            

clear all;close all;
options = optimset('Display','iter');%,'PlotFcns',@optimplotfval);
salida = fopen('output.txt','w');
global xx; xx=[];

figure; plot_f
hold on

x0=1.2;

% La convergencia del metodo numerico depende
% esencialmente del iterante inicial elegido.
% No obstante, nunca va a converger a -7 
% converge a -7, que es 'a simple vista', el minimo
% global del problema con restricciones.

%Convergencias:
% x0 = -5;  % xmin = -7.852. 
% x0 = -3;  % xmin = -1.850.
% x0 = 5;   % xmin = 4.931.
% x0 = 10;  % xmin = 10.007. 

% Cambiar el solver local segun se
% desee: fminsearch o fminunc

f=@(x)f(x);
tic
[xmin,fmin,exitflag,outputs] = fminsearch('f',x0,options);
t1 = toc;
p4 = plot(x0,f(x0),'sq','MarkerSize',8,'MarkerFaceColor',[0 1 1]);
hold on
p5 = plot(xx(:,1),xx(:,2),'ro','MarkerSize',3);
hold on
p6 = plot(xmin,f(xmin),'o','MarkerSize',5,'MarkerFaceColor',[1 1 0]);
hold on
legend([p4,p5,p6],{'Iterante inicial','Iterantes','Optimo local'})
hold off

fprintf(salida,'\n');
fprintf(salida,'Solucion con optimizador local:');
fprintf(salida,'\n');
fprintf(salida,'Solucion optima: xmin = %.3f.' ,xmin);
fprintf(salida,'\n');
fprintf(salida,'Valor de f: fmin = %.3f.',fmin);
fprintf(salida,'\n');
fprintf(salida,'Evaluaciones de la funcion objetivo: k = %i.',outputs.funcCount);
fprintf(salida,'\n');
fprintf(salida,'Tiempo total: t1 = %.3f.',t1);
fprintf(salida,'\n');
fprintf(salida,'Iteraciones del metodo: n = %i',outputs.iterations);
fprintf(salida,'\n');
fprintf(salida,'\n');




function f=f(x)
    global xx;
    f = 0.1.*x.^3+12.*sin(x)+1.7.^(-x)-x.^2;
    xy = [x,f];
    xx = [xx; xy];
end

However, I'm just overwriting the data which is currently in the plot's legend. How can I solve this?

Answer 1

[Sergey Kasyanov]

Hello!

The simplest way is to define 'DisplayName' parameter for curves. For example:

plot(-7.000,f(-7.000),'sq','MarkerSize',8,'MarkerFaceColor',[1 0 0], 'DisplayName', 'Función');
%...
%...
%...
p4 = plot(x0,f(x0),'sq','MarkerSize',8,'MarkerFaceColor',[0 1 1], 'DisplayName', 'Iterante inicial');

After that all you need to eval:

legend show

[Manuel López]

It works!! Thank you :)

Answer 2

[Alan Stevens]

You might have to change the plot order a little. More like this perhaps:

M=1000;
x=linspace(-11,15,M);
y=linspace(-7,11,M);

f1=0.1.*x.^3+12.*sin(x)+1.7.^(-x)-x.^2;
f2=0.1.*y.^3+12.*sin(y)+1.7.^(-y)-y.^2;
f=@(x)(0.1.*x.^3+12.*sin(x)+1.7.^(-x)-x.^2);
x0 = 1.2;
[xmin,fmin,exitflag,outputs] = fminsearch(f,x0);


plot(x,f1,'Color','b'); hold on;
plot(y,f2,'Color',[0,1,0],'LineWidth',3);
plot(x0,f(x0),'o','MarkerSize',8,'MarkerFaceColor',[0 1 1]);
plot(-7.000,f(-7.000),'sq', ...
     -1.850,f(-1.850),'sq', ... 
     4.931,f( 4.931),'sq', ...  
     10.007,f(10.007),'sq','MarkerSize',8,'MarkerFaceColor',[1 0 0]);
legend('Función', 'Función en [-7,11]','Iterante inicial','Óptimos locales')

xlim([-15 15])
ylim([-70 80])
ax = gca;
ax.XAxisLocation = 'origin';
ax.YAxisLocation = 'origin';
box off