title: R geom_line not plotting as expected
body: <p>I am using the following code to plot a stacked area graph and I get the expected plot.</p>
  
  <pre><code>P &lt;- ggplot(DATA2, aes(x=bucket,y=volume, group=model, fill=model,label=volume)) +  #ggplot initial parameters
    geom_ribbon(position='fill', aes(ymin=0, ymax=1))
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/s7QEM.jpg" alt="area plot no lines"></p>
  
  <p>but then when I add lines which are reading the same data source I get misaligned results towards the right side of the graph</p>
  
  <pre><code>P + geom_line(position='fill',  aes(group=model, ymax=1))
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/n6on8.jpg" alt="enter area plot with lines"></p>
  
  <p>does anyone know why this may be? Both plots are reading the same data source so I can't figure out what the problem is.</p>