Adding Legend to a multiple graph within a loop

Hello there!

I am writing a short code for plotting data from COMSOL.

These data concern the attenuation loss of a bent loss for fifteen curvature radii against twenty-seven wavelength forming a 405 X 3 matrix. I need to overlay each plot within the same image and to label each one by the relative curvature radius. I succeeded to complete the first part of the task but I really cannot add the legends. Could anyone please help me?

clear all

close all

clc

hold on

data=dlmread('data.txt')

for i= 1:27:378

for j = 28:27:405

for k=1:15

txt = ['X = ',num2str(k)];

plot(data(i:j,2),data(i:j,3), 'DisplayName' ,txt)

end

end

end

Answer 1

[Tommy]

The legend should show after you call legend(), i.e.:

clear all
close all
clc
hold on
data=dlmread('data.txt')
for i= 1:27:378
    for j = 28:27:405
        for k=1:15                
            txt = ['X = ',num2str(k)];
            plot(data(i:j,2),data(i:j,3), 'DisplayName' ,txt)
        end     
    end
end
legend

But I believe this will create 14*14*15 = 2940 separate line plots. Are you possibly aiming for this instead?

plot(data(1:27,2),data(1:27,3), 'DisplayName', ['X = 1'])
plot(data(28:54,2),data(28:54,3), 'DisplayName', ['X = 2'])
.
.
.
plot(data(379:405,2),data(379:405,3), 'DisplayName', ['X = 14'])

If so, you could use this:

hold on
data=dlmread('data.txt')
for k = 1:15
    txt = ['X = ',num2str(k)];
    i = 27*(k-1)+1;
    j = 27*k;
    plot(data(i:j,2),data(i:j,3),'DisplayName',txt)
end
legend

[Nico Pisani]

Thank you!

It works! Is there a way to select colours for each curvature radius?

Nico

[Tommy]

Happy to help!

Sure, you can set the Color when calling plot:

hold on
data=dlmread('data.txt')
colors = rand(15,3);
for k = 1:15
    txt = ['X = ',num2str(k)];
    i = 27*(k-1)+1;
    j = 27*k;
    plot(data(i:j,2),data(i:j,3),'DisplayName',txt,'Color',colors(k,:))
end
legend

This just creates 15 random RGB triplets. You could set them yourself to specific colors if you'd like, or you could use a colormap to generate the RGB triplets.

[Nico Pisani]

Thank you, Tommy. This helps!

Cheers!