How to add a legend for a plot generated with a function multiple times?

I am working with orbits around Earth. To plot them, I use a function with the orbital parameters as input. My problem is that I don't know how to create a legend when calling the function more than one time to show on the same plot multiple orbits.

Adding a legend manually like this

plotOrbit(a, e, i, OM, om, th0, thf, dt, mu)
plotOrbit(a1, e1, i1, OM1, om1, th0, thf, dt, mu)

legend("Initial orbit", "Final orbit")

give me a wrong line for the second orbit. (It should be orange instead of a random blue tiny line).

I tried to follow a different approach

txt = 'Initial orbit';
plotOrbit(a, e, i, OM, om, th0, thf, dt, mu, txt)
txt = 'Final orbit';
plotOrbit(a1, e1, i1, OM1, om1, th0, thf, dt, mu, txt)
legend show

Adding this line in the function script

plot3(r(1, :), r(2, :), r(3, :), 'DisplayName',txt, LineWidth=2)

Now the legend shows the right lines, but the result shows 4 extra labels that I don't know how to remove.

ù

Do you know how to solve this? Thank you

[Steven Lord]

It's going to be difficult to offer any specific suggestions without seeing what your plotOrbit function is doing.

[Niccolò Bruno]

Even if @Antoni Garcia-Herreros helped me already, I add the function for completeness.

function plotOrbit(a, e, i, OM, om, th0, thf, dt, mu)

r = [];
for t = th0:dt:thf
    r = [r, parorb2rv(a, e, i, OM, om, t, mu)]; 
end
% this gives the position in a cartesian frame in the form r = [x; y; z]

figure(1)
plot3(r(1, :), r(2, :), r(3, :), LineWidth=2)
axis equal;     % Make the axes scales match
title("Orbits");
hold on;        % Add to the plot
Terra3d         %function to add the 3d model of the Earth
end

Answer 1

[Antoni Garcia-Herreros]

Hello,

As @Steven Lord pointed out it's hard to suggest anything without knowing how plotOrbit works, but you could try something like this:

plotOrbit(a, e, i, OM, om, th0, thf, dt, mu)
plotOrbit(a1, e1, i1, OM1, om1, th0, thf, dt, mu)
l=legend('Initial orbit','','','Final orbit');

[Niccolò Bruno]

Thank you! This works perfectly