title: how to find Eigenvalues for non quadratic matrix
body: <p>I want to make similar graphs to this given on the picture:
  <img src="https://i.stack.imgur.com/8Qtx1.png" alt="enter image description here"></p>
  
  <p>I am using Fisher Iris data and employ PCA to reduce dimensionality.
   this is code:</p>
  
  <pre><code>load fisheriris
  [pc,score,latent,tsquare,explained,mu] = princomp(meas); 
  </code></pre>
  
  <p>I guess the eigenvalues are given in Latent, that shows me only four features and is about reduced data.</p>
  
  <p>My question is how to show all eigenvalues of original matrix, which is not quadratic (150x4)? Please help! Thank you very much in advance!</p>