title: Creating a color map / heatmap in Matlab / Octave
body: <p>I'm using Octave 3.8.1 which is like Matlab and I'm trying to create a color map / heatmap to look something like this</p>
  
  <p><a href="https://i.stack.imgur.com/dAFPL.png" rel="noreferrer"><img src="https://i.stack.imgur.com/dAFPL.png" alt="Map"></a></p>
  
  <p>I have an array <strong>a1</strong> where the 1st col is x, the 2nd col is y and the 3rd col is intensity.  I know I can plot a 2d plot using plot(x,y) but how do I add / show the intensity (the 3rd col) in the plot.</p>
  
  <pre><code>a1=
  [225.512    2.64537 0.00201692
  225.512 2.64537 0.00201692
  226.94  1.59575 0.00225557
  226.94  1.59575 0.00225557
  227.31  1.70513 0.002282
  227.31  1.70513 0.002282
  227.729 5.34308 0.00205535
  227.729 5.34308 0.00205535
  227.975 5.12741 0.001822
  227.975 5.12741 0.001822]
  </code></pre>
  
  <p>Full dataset is located here <a href="https://www.dropbox.com/s/mmhpbelnjoondho/full.csv" rel="noreferrer">https://www.dropbox.com/s/mmhpbelnjoondho/full.csv</a></p>
  
  <p>Please note that this is just sample data.</p>