MATLAB: Legend does not have the right color every two plots.

colorlegendMATLABplot

%Every even plot inside the "for" has a mismatch in color(and the mismatches have the same color). 
%I'm plotting from simulink. Tried fixing using the vector "cor" inthe plot but didn't help.
clear all
close all
clc
legend('off');
legend('show');
Vref=0.1;
gamma=0.1;
Kd=1:1:6;
Kp=1:1:6;
Ki=1:1:6;
cor=[[1 1 0]; [1 0 1]; [0 1 1]; [1 0 0]; [0 1 0]; [0 0 1]; [0 0 0]]
for i = 1:size(Kd,2)
    K_d=Kd(i);
    for j= 1:size(Kp,2)
        K_p=Kp(j);
        info=sim('diagrama_blocos');
        Vt_out=info.Vt.signals.values(:,1);
        Vt_ref_out=info.Vt.signals.values(:,2);
        time_out=info.Vt.time;
        plot(time_out,Vt_out,'LineWidth',2,'Color', cor(j,:));grid on;hold all;
        line([time_out(1),time_out(end)],[Vref,Vref]);
        legendInfo{j}=['Kp= ', num2str(K_p)];
        title(['Curvas para Kd= ', num2str(K_d)]);
    end
    legend(legendInfo)
    figure()
end

Best Answer

"Legend does not have the right color every two plots"

That's because you're adding two lines on each iteration of your loop.

for i = 1:size(Kd,2)
    K_d=Kd(i);
    for j= 1:size(Kp,2)
        K_p=Kp(j);
        info=sim('diagrama_blocos');
        Vt_out=info.Vt.signals.values(:,1);
        Vt_ref_out=info.Vt.signals.values(:,2);
        time_out=info.Vt.time;
        
        % LINE 1
        plot(time_out,Vt_out,'LineWidth',2,'Color', cor(j,:));grid on;hold all;
        
        % LINE 2
        line([time_out(1),time_out(end)],[Vref,Vref]);
        
        legendInfo{j}=['Kp= ', num2str(K_p)];
        title(['Curvas para Kd= ', num2str(K_d)]);
    end
    legend(legendInfo)
    figure()
end

Instead of including any and all objects on your legend, and instead of storing a list of legend strings separately from their corresponding objects, use this 2-step method defined in this answer. The result will look something like this (see inline comments for details,

% Don't do this
%     clear all
%     close all
%     clc
%     legend('off');
%     legend('show');
Vref=0.1;
gamma=0.1;
Kd=1:1:6;
Kp=1:1:6;
Ki=1:1:6;
cor=[[1 1 0]; [1 0 1]; [0 1 1]; [1 0 0]; [0 1 0]; [0 0 1]; [0 0 0]]
for i = 1:size(Kd,2)
    K_d=Kd(i);
    
    % Create figure here
    figure()
    % Set this stuff prior to the j-loop
    grid on
    hold on
    % Preallocate the plot handles
    plotHandles = gobjects(1,size(Kp,2)); 
    
    for j= 1:size(Kp,2)
        K_p=Kp(j);
        info=sim('diagrama_blocos');
        Vt_out=info.Vt.signals.values(:,1);
        Vt_ref_out=info.Vt.signals.values(:,2);
        time_out=info.Vt.time;
        % 1) Store output handles and 2)Define DisplayName propery
        plotHandles(j) = plot(time_out,Vt_out,'LineWidth',2,'Color', cor(j,:), ...
            'DisplayName', ['Kp= ', num2str(K_p)]);  
        
        % Move this out of the j-loop
        %grid on;hold all;
        
        line([time_out(1),time_out(end)],[Vref,Vref]);
        
        % No need for this anymore
        % legendInfo{j}=['Kp= ', num2str(K_p)];
        
        % Move this outside of the loop
        % title(['Curvas para Kd= ', num2str(K_d)]);
    end
    
    % Set title
    title(['Curvas para Kd= ', num2str(K_d)]);
    
    % Call legend with list of handles
    legend(plotHandles)
    
    % Move this to before the j-loop
    % figure()
end

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