title: Generate a graph from CSV using gnuplot
body: <p>I'm getting an error: </p>
  
  <p><em>Skipping data file with no valid points</em></p>
  
  <p>when trying to generate a graph from a csv file using gnuplot, any help is much appreciated!</p>
  
  <p>sample.csv</p>
  
  <pre><code>timestamp,unit,maximum,average
  Thu Jan 29 10:57:00 GMT 2015,Percent,22.96,7.723999999999999
  Thu Jan 29 10:52:00 GMT 2015,Percent,62.79,26.227999999999998
  Thu Jan 29 10:47:00 GMT 2015,Percent,46.54,15.075999999999999
  </code></pre>
  
  <p>run_gnuplot.sh</p>
  
  <pre><code>#!/bin/bash
  gnuplot &lt;&lt; eor
  set terminal png 
  set output 'output.png'
  set style data linespoints
  set datafile separator ","
  set xlabel "timestamp"
  set ylabel "percent"
  plot "sample.csv" using 1:3 title "Maximum" using 1:4 title "Average"  
  eor
  </code></pre>
  
  <p>Error:</p>
  
  <pre><code>bash-4.1$ ./run_gnuplot.sh 
  Could not find/open font when opening font "arial", using internal non-scalable font
  
  gnuplot&gt; plot "sample.csv" using 1:3 title "Maximum" using 1:4 title "Average"  
                                             ^
           line 0: warning: Skipping data file with no valid points
  
  gnuplot&gt; plot "sample.csv" using 1:3 title "Maximum" using 1:4 title "Average"  
                                                       ^
           line 0: x range is invalid
  </code></pre>