title: How to draw multiple centric circles in R
body: <p>Hey I want to draw several circles in R with different radius.</p>
  
  <p>I did this with 'plotrix' and draw.circle:</p>
  
  <pre><code>draw.circle (0,0,1)
  draw.circle (0,0,1.5)
  draw.circle (0,0,2)
  ...
  </code></pre>
  
  <p>Do you know a faster and smarter way to do that?</p>