title: gnuplot: 2D plot of a matrix of data
body: <p>How can I plot (a 2D plot) a matrix in Gnuplot having such data structure, using the first row and column as a x and y ticks (the first number of the first row is the number of columns) and represent the rest of the values by a colour mapping so it can be seen on a 2D plane ?</p>
  
  <pre><code>4 0.5 0.6 0.7 0.8
  1 -6.20 -6.35 -6.59 -6.02
  2 -6.39 -6.52 -6.31 -6.00
  3 -6.36 -6.48 -6.15 -5.90
  4 -5.79 -5.91 -5.87 -5.46
  </code></pre>