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Legend for multiple plots

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I want to generate a legend for multiple plots on the same figure using 'hold on;'. I am using a certain method I found through googling but I am not getting expected results. Here is my code.
sf = 1; % scaling factor
lambda_b = 10; % BS process density
lambda_c = 10; % cluster process density c <= b
lambda_u = 50; % user process density; large enough to make each BS active
% Base station process
npointsb = poissrnd(lambda_b*sf); % poisson variable; no. of points
pprocb = rand(npointsb,2); % uniform dist of points
xb = pprocb(:,1);
yb = pprocb(:,2);
% Cluster process
npointsc = poissrnd(lambda_c*sf);
pprocc = rand(npointsc,2);
xc = pprocc(:,1);
yc = pprocc(:,2);
% User process
npointsu = poissrnd(lambda_u*sf);
pprocu = rand(npointsu,2);
xu = pprocu(:,1);
yu = pprocu(:,2);
[vxb,vyb] = voronoi(xb,yb);
[vxc,vyc] = voronoi(xc,yc);
p1 = plot(vxb,vyb,'b','userdata','BS tessellation'); hold on;
p2 = plot(xb,yb,'rs','userdata','BS');
p3 = plot(vxc,vyc,'r','userdata','Cluster tessellation');
p4 = plot(xu,yu,'go','userdata','User'); hold off;
legend(get(gca, 'children'), get(get(gca, 'children'), 'userdata'));
axis([0 1 0 1]);
The result of this code is illustrated in the image.
You can see there are multiple entries and I suspect that is because the variables returned by the voronoi function are matrices and not vectors like the other variables. It seems this is making the plot function return a column vector of Line objects and this is why I am getting the multiple legend entries.
How do I get around this and plot the correct legend ignoring the multiple entries?
  1 Comment
Vijayanand Sivakumar
Vijayanand Sivakumar on 28 Mar 2021
Thank you very much for the solution.

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Accepted Answer

Jonathan Mayers
Jonathan Mayers on 20 Jul 2016
Hi all,
I have obtained the desired legend output using handles. See the code below. The code generating the points did not change.
[vxb,vyb] = voronoi(xb,yb);
[vxc,vyc] = voronoi(xc,yc);
p1 = plot(vxb,vyb,'b'); hold on;
p2 = plot(xb,yb,'rs');
p3 = plot(vxc,vyc,'r');
p4 = plot(xu,yu,'go'); hold off;
axis([0 1 0 1]);
% Create column vector of plot handles
% Variables returned from voronoi are matrices and plotting them
% returns a column vector of handles so extract the first one
h = [p1(1);p2;p3(1);p4];
% Now call the legend function passing the handle h and specify the text
legend(h,'BS tessellation','BS','Cluster tessellation','User');
The below image verifies correct output of the code.
Tingmingke Lu
Tingmingke Lu on 30 Jun 2020
This comes in handy! Thanks!

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More Answers (2)

Taniel Winner
Taniel Winner on 24 Jul 2021
I have found this code INCREDIBLY HELPFUL!!! It works!! Download it!

Miguel Marques
Miguel Marques on 23 May 2019
You are my hero too.

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