How can I show all the plotted lines in the legend?

Hi, I have obtained the figure from a program as shown below. In general, the figure contains the actual data,data fit and four polynomial curves ,4um(red),5um(yellow),6um(blue),7um(green). However, the legend just showed one line, red(4um). I want to display in the legend all other three missing lines, yellow, blue and green.

%%
clc
clear all
load data.mat

for i=1:(length(dep(1,:)))
    PP(:,i)=plot(dep(:,i),ext','ok','LineWidth',2)% original data
    hold on
    P1(:,i) = polyfit(dep(:,i),ext,2);%%2 indicates the quadratic
    % x_values =  min(in_(1,:)): 0.001:max(x_axis(1,:));
    Y= polyval(P1(:,i),dep(:,i));
    h1 = plot(dep(:,i),Y,'*g','LineWidth',1) % fitted
    hold on
    Y1 = polyval(P1(:,i),dep(:,i));
    R1 =  corrcoef(Y1,dep(:,i));
    hold on
    %%lsline
    ss = min(dep(:,i)) : 0.001: max(dep(:,i));
    Y2 = polyval(P1(:,i),ss);
    col=['r' 'y' 'b' 'g'];
    h2 =  plot(ss,Y2,'color',col(i),'LineWidth',1)
    hold on
    title('Polynomial fitting','FontSize',16,'FontWeight','normal')
    xlabel('Depolarisation ratio \delta_{in}','FontSize',12,'FontWeight','normal');
    ylabel('Extinction coefficient \alpha{(m^-^1)}','FontSize',12,'FontWeight','normal');
    legend('Actual data','Data fit',['Polynomial curve' num2str(i),'\mum'])
    ylim([0.005 0.03])
end

Answer 1

[Adam Danz]

I've cleaned up your code (see inline comments).

You have to supply the legend with handles that specify what belongs in the legend and you have to store the handle from each iteration.

I've made some guesses in in the legend inputs so if it doesn't work right away, play around with it to get what you want.

hold on ;              % MOVE THIS OUTSIDE THE LOOP
col=['r' 'y' 'b' 'g']; % MOVE THIS OUTSIDE THE LOOP
lineHandles = gobjects(1,length(dep(1,:))); % ADD THIS

for i=1:length(dep(1,:))
    PP(:,i)=plot(dep(:,i),ext','ok','LineWidth',2)% original data
    P1(:,i) = polyfit(dep(:,i),ext,2);%%2 indicates the quadratic
    % x_values =  min(in_(1,:)): 0.001:max(x_axis(1,:));
    Y= polyval(P1(:,i),dep(:,i));
    h1 = plot(dep(:,i),Y,'*g','LineWidth',1) % fitted
    Y1 = polyval(P1(:,i),dep(:,i));
    R1 =  corrcoef(Y1,dep(:,i));
    %%lsline
    ss = min(dep(:,i)) : 0.001: max(dep(:,i));
    Y2 = polyval(P1(:,i),ss);
    
    lineHandles(i) =  plot(ss,Y2,'color',col(i),'LineWidth',1);  % STORE HANDLE

end


% MOVE THIS OUTSIDE THE LOOP
title('Polynomial fitting','FontSize',16,'FontWeight','normal')
xlabel('Depolarisation ratio \delta_{in}','FontSize',12,'FontWeight','normal');
ylabel('Extinction coefficient \alpha{(m^-^1)}','FontSize',12,'FontWeight','normal');
ylim([0.005 0.03])

% SUPPLY HANDLES, DEFINE EACH POLY CURVE LINE
legend([PP(1,i), h1, lineHandles],...
    'Actual data','Data fit',compose('PolyCurve %d\mum',1:length(dep(1,:))))

[Wiqas Ahmad]

Thank you for your modification and improvement to my program. The code works well but still needs some modification. I want to display the legend as Actual data(black dot), Data fit (green dot) and four PolyCurves 4,5,6,7um (r,y,b,g). Could you please have a glance again to your code? The figure diplayed by your code can be seen

[Adam Danz]

Try this

legend([PP(1,i), h1, lineHandles],...
    [{'Actual data','Data fit'},compose('PolyCurve %d\mum',1:length(dep(1,:)))])

If that doesn't work, you need to ask yourself, is this a vector of 6 handles?

[PP(1,i), h1, lineHandles]

and is this a vector of 6 legend strings?

[{'Actual data','Data fit'},compose('PolyCurve %d\mum',1:length(dep(1,:)))]