title: GNUPLOT: How to set reverse HOT color palette
body: <p>Here is the example in <a href="http://gnuplot.sourceforge.net/demo/pm3dcolors.html" rel="noreferrer">http://gnuplot.sourceforge.net/demo/pm3dcolors.html</a></p>
  
  <pre><code>set palette rgb 21,22,23; set title "hot (black-red-yellow-white)";
  </code></pre>
  
  <p>The above code set the hot palette. However I want a reversed hot palette, say:</p>
  
  <p>white-yellow-red-black.</p>
  
  <p>Small least value map to white and largest value map to black.</p>