Help with create Root Locus

Hello I need to build a function that will print a Root Locus without using the function of rlocus. this my code but I have missed something to get to the right answer.I would like if someone can fix my code or give me another code that works and create a root locus of random Transfer Function.Thanks. the code is:

clc;

s=tf('s');

   k=0:0.1:20;

   help pzmap

for i=1:1:length(k)

   G=zpk([],[-5 2],1)

feedback(G,1)

pzmap(G)

end

hold off;

plot(real(G),imag(G))

Answer 1

[Sebastian Castro]

There is actually an rlocus function in Control System Toolbox.

>> rlocus(G)

If you want to do all the work yourself for some other reason:

k=0:0.1:20;
for idx = 1:numel(k)
  closedLoop = feedback(G,k(idx));
  p(:,idx) = pole(closedLoop);
end

figure
hold on
plot(real(p'),imag(p'))

- Sebastian