title: How to make points one color when a third column equals zero, and another color otherwise, in Gnuplot?
body: <p>I need to vary the point color for a row of values based on the color in one column. The data:</p>
  
  <pre><code># x y z
  1, 3, 0  
  1, 5, 6  
  3, 5, 2  
  4, 5, 0
  </code></pre>
  
  <p>The color should be one value if the column is zero and a different color if the value in the third column is non-zero. </p>
  
  <p>So, I'm assuming:</p>
  
  <pre><code>plot "./file.dat" u 1:2:3 with points palette
  </code></pre>
  
  <p>as found here: <a href="https://stackoverflow.com/a/4115001">https://stackoverflow.com/a/4115001</a> will not quite work.</p>
  
  <p>In the above example data, that gnuplot command provides three different colors instead of the two I'm looking for.</p>