title: 3D histogram with gnuplot or octave
body: <p>I would like to draw a 3D histogram (with gnuplot or octave) in order to represent my data.
  lets say that I have a data file in the following form:</p>
  
  <pre><code>2 3 4    
  8 4 10    
  5 6 7
  </code></pre>
  
  <p>I'd like to draw nine colored bars (the size of the matrix), in the set [1,3]x[1,3], such that the bar's color is proportional to the bar's height. How can I do this?</p>