title: D3 descending scale
body: <p>Given a set of number 0 to 1, I need a d3 scaling function that returns 0 to 100.</p>
  
  <pre><code>var scale = d3.scale.linear();
  scale.domain([0,1]);
  scale.range([0,100]);
  scale(0.1);  // 10
  </code></pre>
  
  <p>This works great.  However, because I'm setting opacity for data elements based on confidence intervals, I want the output (range) to diminish as the input (domain) increases.</p>
  
  <p>So for example:</p>
  
  <pre><code>scale(0.1);  // should produce 90
  scale(0.2);  // should produce 80
  scale(0.3);  // should produce 70
  </code></pre>
  
  <p>So as the scale input goes up, the output goes down.</p>
  
  <p>How can I instruct the scale object to do this?</p>