title: Gnuplot: line opacity / transparency?
body: <p>I am using Gnuplot to successfully plot some time series data. However, the series are fairly dense (10,000's of samples in about 5 inches of space), and when I plot multiple series, it is hard to see underneath the series that was plotted on top. <strong>Is there any way to make the lines have a bit of opacity or transparency (i.e. make the line transparent so underneath lines are visible)?</strong></p>
  
  <p>Excel has this capability, but I would much prefer to use Gnuplot.</p>
  
  <p>Below is a sample of what I'm talking about. You can't see the red lines under the green lines. I would actually like to add a third time series. I am plotting with the command:</p>
  
  <pre><code>plot [][-3:3] 'samples_all.csv' using 1:7 title 'horizontal' w l ls 1, '' using 1:8 title 'vertical' w l ls 2"
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/Atneo.png" alt="enter image description here"></p>