title: delete vector entries based on another vector
body: <p>I have two vectors</p>
  
  <pre><code>a &lt;- c(1:20)
  b &lt;- c(2,11,14)
  </code></pre>
  
  <p>I want to delete the entries in the a vector based on the vector entries in b (I want the 2nd, 11th, and 14th entries deleted).</p>
  
  <p>I've tried several methods, including:</p>
  
  <pre><code>c &lt;- a[!a %in% b]
  </code></pre>
  
  <p>but that doesn't work.</p>
  
  <p>Any suggestions? I've tried searching SO, but can only find deleting based on values.</p>