How to make a legend for a plot within a for loop

HI! I am currently plotting a graph (with 3 different entries) and I want to create a legend within the for loop that would show each iteration for the 3 different I/O how should I approach this? The current legend i have does not update with each iteration

[Will Fritz]

Hi, can you provide a little more context to your issue. For example, do you have three different plots? Or just one where the legend changes every iteration? Any code provided to help frame this would be appreciated

[Sue MM]

I have 2 bode plots that I am plotting on the same figure within the for loop.

figure(1)
bode(sys1)
grid on 
hold on 
margin(sys2)

I am trying to create a legend that will distinguish between each iteration of the bode plot that it is printing

Answer 1

[Adam Danz]

It's strange that bode() doesn't seem to output the plot handles.

Anyway, here are two options using fake data; the first is best if your code can be adapted to it.

Fake data

H1 = tf([1 0.1 7.5],[1 0.12 9 0 0]);
H2 = tf([1 0.3 7.5],[1 0.12 9 0 0]);
H3 = tf([1 0.5 7.5],[1 0.12 9 0 0]);

Option 1: no loop

bode(H1, 'r', H2, 'b', H3, 'k')
legend({'H1', 'H2', 'H3'})

Option 2: with loop * you have to 'hold' your axes!

values = {H1, H2, H3};
H = values{1}; 
figure()
bode(H)
axh = findall(gcf, 'type', 'axes');
hold(axh(3),'on') % upper axis
hold(axh(2),'on') % lower axis
for i = 2:numel(values)
    bode(values{i})
end
 legend(axh(3), {'H1', 'H2', 'H3'}) % upper axis
 legend(axh(2), {'H1', 'H2', 'H3'}) % lower axis

[Sue MM]

Thanks!!