title: Plot vector field expressed in polar coordinates with quiver in MATLAB
body: <p>I want to plot the following vector field expressed in polar coordinates:</p>
  
  <pre><code>E = r * R  % (i am using big R to represent r^ hat). 
  </code></pre>
  
  <p>The field should look something like <a href="http://em.eecs.umich.edu/pdf/ulaby_solved_problems.pdf" rel="nofollow noreferrer">figure P3.20</a>:</p>
  
  <p><a href="https://i.stack.imgur.com/QBvV7.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/QBvV7.png" alt="enter image description here"></a></p>