title: How can I plot a cumulative distribution function (CDF) for binned data?
body: <p>I've got discrete data which i presented in ranges
  for example</p>
  
  <pre><code>         Marks Freq cumFreq 
  1  (37.9,43.1]    4       4    
  2  (43.1,48.2]   16      20   
  3  (48.2,53.3]   76      96    
  </code></pre>
  
  <p>i need to plot the cmf for this data, I know that there is</p>
  
  <pre><code>plot(ecdf(x))
  </code></pre>
  
  <p>but i don't what to add for it to have what I need.</p>