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

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Sue MM
Sue MM 2018-7-18
编辑： Adam Danz 2021-1-6
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
  2 个评论
Will Fritz
Will Fritz 2018-7-18
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
Sue MM 2018-7-18
编辑：dpb 2018-7-18
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

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Adam Danz
Adam Danz 2018-7-18
编辑：Adam Danz 2021-1-6
Ran in:
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

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