title: Read data in Gnuplot
body: <p>I have a file with a matrix like :</p>
  
  <pre><code>1 2 3
  4 5 6
  7 8 9
  </code></pre>
  
  <p>Using gnuplot, I would like to extract the Variable in the 3th row on the 2th column, and store it in a variable called X for example. please how to do that using gnuplot.
  Thanks  </p>