title: How to tell what is in one vector and not another?
body: <p>In matlab there is a way to find the values in one vector but not in the other.</p>
  
  <p>for example:</p>
  
  <pre><code>x &lt;- c(1,2,3,4)
  y &lt;- c(2,3,4)
  </code></pre>
  
  <p>is there any function that would tell me that the value in <code>x</code> that's not in <code>y</code> is 1?</p>