title: ploting gnuplot and divide operation by zero
body: <p>I am using gnuplot to build a graph but some of my lines are zero and I am making a math with two columns. Divide any number by zero is throwing a error when I try to plot my file.</p>
  
  <pre><code>set output "iostat-iops.png"
  set title "IOPs - KBytes per IO"
  set xdata time
  set timefmt "%H:%M:%S"
  set format x "%H:%M"
  plot "iostat-x.dat.1" using 2:($9/$7) title "rkb/s" with linespoints, \
  "iostat-x.dat.1" using 2:($10/$8) title "wkb/s" with linesponints
  </code></pre>
  
  <p>In my example I have the column 7 with zero sometimes. Is there a way to make a IF on it?</p>