# Legend colours are different from the plot

3 views (last 30 days)
UserCJ on 29 Sep 2022
Commented: Star Strider on 29 Sep 2022
I'm trying to create a plot for different ϕ values with respect to and x for a function(f) when . I'm also creating the legend inside the loop. The code is working, but the legend colours are not matching with the plot.
clear all;
clc;
[x,xi] = meshgrid(0:0.001:1,0:0.002:1);
b = 3;
a = 1;
nphi = 7;
phi= [0 0.4 0.8 1 1.4 1.8 2];
for p = 1:nphi
f2 = @(x,a,b) a*b*(x)./(b-(1-x));
f1 = @(x,a,b) a*b*(1-x)./(b-x);
r = @(x,xi,a,b,phi) (1-(phi./2)).*xi.*f1(x,a,b) - (phi./2).*(1-xi).*f2(x,a,b);
R = r(x,xi,a,b, phi(p));
M_phi=contour(x,xi,R,[0 0]);
figure(2)
plot(M_phi(1,2:end),M_phi(2,2:end),'Linewidth',2)
legendInfo{p} = ['$\phi=$' num2str(phi(p))];
legend(legendInfo,'interpreter','latex',Location="southeast")
hold on
end
hold off
xlabel('$x$','interpreter','latex')
ylabel('$x_i$','interpreter','latex')
Here is the output of the function and there are multiple legend values with blue and there are only two plot with blue in the plot.
##### 2 CommentsShowHide 1 older comment
UserCJ on 29 Sep 2022
@Star Strider Thanks for that! I edited the code. "rs_a" is not a function, it is just this;
r = @(x,xi,a,b,phi) (1-(phi./2)).*xi.*f1(x,a,b) - (phi./2).*(1-xi).*f2(x,a,b);

Star Strider on 29 Sep 2022
Thank you for the ‘r’ anonymous function! I can now run your code.
The code was plotting the contours as well as the ϕ vectors. I changed the code to return only the line handles (the ‘hp{p}’ outputs of the plot calls), and added the 'DisplayName' to each plot call to avoid any ambiguity. I also ‘stepped through’ the loop with increasing values of the ‘nphi’ value to be certain that your code works as it should. It now appears to. (I also made some aesthetic tweaks.)
I’ll keep working on this if there is more to be done.
Try this —
% clear all;
% clc;
[x,xi] = meshgrid(0:0.001:1,0:0.002:1);
b = 3;
a = 1;
nphi = 7;
phi= [0 0.4 0.8 1 1.4 1.8 2];
for p = 1:nphi
f2 = @(x,a,b) a*b*(x)./(b-(1-x));
f1 = @(x,a,b) a*b*(1-x)./(b-x);
r = @(x,xi,a,b,phi) (1-(phi./2)).*xi.*f1(x,a,b) - (phi./2).*(1-xi).*f2(x,a,b);
R = r(x,xi,a,b, phi(p));
M_phi=contour(x,xi,R,[0 0]);
figure(2)
hp{p} = plot(M_phi(1,2:end),M_phi(2,2:end),'Linewidth',2, 'DisplayName',sprintf('$\\phi = %4.1f$',phi(p)));
% legendInfo{p} = ['$\phi=$' num2str(phi(p))];
% legend(legendInfo,'interpreter','latex',Location="southeast")
legend([hp{:}],'interpreter','latex',Location="southeast")
hold on
end
hold off
xlabel('$x$','interpreter','latex')
ylabel('$x_i$','interpreter','latex')
.
##### 2 CommentsShowHide 1 older comment
Star Strider on 29 Sep 2022
As always, my pleasure!

### More Answers (1)

vamshi sai yele on 29 Sep 2022
Edited: vamshi sai yele on 29 Sep 2022
I have tried to run the code from my end but due to insufficient initializations I couldn't run to check the issue on first hand. Solution would have been more precise if code ran from my end
However, I have couple of suggestions to set this up.
Scenario-1
Assigning the name/title to the plot and then declaring the 'legend' will display in the necessary order. Below is snipet for the same.
Scenario-2
Mentioning the titles directly in the 'legend' function directly in the intended order as shown.
##### 1 CommentShowHide None
UserCJ on 29 Sep 2022
In my situation, the legend is automatically created inside the loop. As you can see, all the values appear to be correct, but the colours are not correct with the plot colour. I know how to add manually if it's known, but this is looping over somne values and the legend is created inside it.

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