title: How to plot the root locus of a complex transfer function?
body: <p>I am having issues trying to get the root locus plot for the following complex transfer function (H):</p>
  
  <pre><code>% Ax = b Form
  A =    1.0e+06 *[0.0713 - 0.0073i,...
                   -1.8793 - 0.0357i];
  b = -32.4298;
  
  %TF
  G = A\b;
  
  %PI controller gain
  Kp = 100; %proportional gain      
  Ki = 1; %integral gain
  K = pid(Kp,Ki);  %PI controller
  
  %Open Loop TF
  H = G*K;
  
  rlocus(G)
  </code></pre>
  
  <p>The error I get is the following: 
  "Cannot compute the root locus of models with complex data."</p>
  
  <p>Can I just drop the imaginary parts of the TF (shown below) to do the root locus?</p>
  
  <pre><code>   (0.001725-3.277e-05i) s + (1.725e-05-3.277e-07i)
   ------------------------------------------------
                            s
  </code></pre>