title: Selective Opacity in MapBox
body: <p>I'm currently trying to set the opacity of individual units in a given layer. Based on <a href="https://stackoverflow.com/questions/60872832/mapbox-gl-js-set-paint-property-on-specific-feature-in-layer">this question</a>, I am creating a filter to get the right units – which works properly when selecting the same units for setting individual patterns – and attempting to set the opacity value accordingly. My filter is the following MapBoxGL style expression:</p>
  <pre><code>filter = [
      &quot;in&quot;,
      [&quot;get&quot;, &quot;GEOID20&quot;],
      [&quot;literal&quot;, geoids],
      1/3, 0
  ]
  </code></pre>
  <p>Based on my understanding of style expressions, this <em>should</em> set the opacities of the units found by the query to 1/3, and set all others to 0. However, I consistently get the same JS error:</p>
  <p><code>Error: layers.browse_in_vtds20.paint.fill-opacity: Expected 2 arguments, but found 4 instead.</code></p>
  <p>Where am I going wrong here? The above expression works for setting colors/patterns individually, why shouldn't it work for setting opacities?</p>