title: get the derivative of an ECDF
body: <p>Is it possible to differentiate an ECDF? Take the one obtained in the following  for example example.</p>
  
  <pre><code>set.seed(1)
  
  a &lt;- sort(rnorm(100))
  b &lt;- ecdf(a)
  
  plot(b)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/Dnr9z.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Dnr9z.png" alt="enter image description here"></a></p>
  
  <p>I would like to take the derivative of <code>b</code> in order to obtain its probability density function (PDF).</p>