title: Gnuplot smooth confidence band
body: <p>According to the answer given in this question <a href="https://stackoverflow.com/questions/25512006/gnuplot-smooth-confidence-interval-lines-as-opposed-to-error-bars/25512858?noredirect=1#comment48933581_25512858">Gnuplot smooth confidence interval lines as opposed to error bars</a> I was able to get the same result for my data given by (the error of y is symmetric so it is y plus/minus errorY):</p>
  
  <pre><code># x y errorY   
  1   3   0.6 
  2   5   0.4  
  3   4   0.2
  4   3.5 0.3
  </code></pre>
  
  <p>Code:</p>
  
  <pre><code>set style fill transparent solid 0.2 noborder
  plot 'data.dat' using 1:($2-$3):($2+$3) with filledcurves title '95% confidence', \
       '' using 1:2 with lp lt 1 pt 7 ps 1.5 lw 3 title 'mean value'
  </code></pre>
  
  <p>Now the confidence band is given by connecting every y+errorY and y-errorY point. I would like it if the connection is not just a straight line, but rather a smooth line, like how one can smoothen data points with <code>smooth csplines</code>..</p>