title: proportional bar plot with ggplot2
body: <p>I have a dataframe d</p>
  <pre><code>&gt; head(d,10)
       age3 num_sint
  1091   25        2
  835    38        0
  993    38        1
  1480   38        0
  1996   38        0
  2216   38        0
  3126   38        0
  3931   38        0
  6479   38        0
  6784   38        0
  </code></pre>
  <p>Where num_sint is a variable between 0 and 8.
  I would like to plot something like this</p>
  <p><img src="https://i.stack.imgur.com/e8Lc8.png" alt="enter image description here" /></p>
  <p>With age3 on the x axis and on the y axis the proportion.</p>
  <p>All the columns should go from 0 to 1</p>
  <p>The column for age3=25 would be all red (because 100%=2).
  The column for age3=38 would be something like 10% blue and 90% green.</p>
  <p>I spent a lot of time on this. Is there any easy solution?</p>