title: Plotting multiple series from file using Gnuplot
body: <p>I've got a data file of the form:</p>
  
  <pre><code>Series_1 "12-Dec-2011 12:00" 32
  Series_1 "12-Dec-2011 12:01" 29
  Series_1 "12-Dec-2011 12:02" 27
  Series_1 "12-Dec-2011 12:04" 23
  
  Series_2 "12-Dec-2011 12:01" 45
  Series_2 "12-Dec-2011 12:02" 43
  Series_2 "12-Dec-2011 12:04" 38
  </code></pre>
  
  <p>Which I'd like to plot as a number of series on the same plot using gnuplot, but I'm new to gnuplot and I cannot figure out how the <code>using</code> clause should be structured here.</p>
  
  <p>I wanted to plot column 2, date/time as the X axis with column 3 as the Y axis, with subsequent sections being overlaid. Is this possible? Surely the X axis doesn't always have to be in the first column?</p>
  
  <p>I tried:</p>
  
  <pre><code>plot "datafile.dat" using 2:3 title 'Hits'
  </code></pre>
  
  <p>But got the error:</p>
  
  <pre><code>x range is invalid
  </code></pre>
  
  <p>Can anyone show me where I'm going wrong?</p>