title: gnuplot with errorbars plotting
body: <p>The data in my "file.txt" file are as in the following (sample row shown)</p>
  
  <pre><code>31 1772911000 6789494.2537881
  </code></pre>
  
  <p>Note that the second column is the mean and the third is the standard deviation of my
  input sample. So, for the error bar, I would need the bar at the x axis value 31, with the error bar start at (second column value)-(third column value), and end at (second column value)+(third column value). I tried the following:</p>
  
  <pre><code>plot "file.txt" using ($1-$2):1:($2+$1) with errorbars
  </code></pre>
  
  <p>but the result is inappropriate. Any help?</p>