title: Apply Filter from one Crossfilter dataset to another Crossfilter
body: <p>I have two datasets that have similar columns/dimensions but are grouped differently by row and contain different measures.</p>
  
  <p>Ex:</p>
  
  <p>Dataset 1</p>
  
  <pre><code>Year   Category   SubCategory    Value01    Value02
  2000   Cars       Sport          10         11
  2000   Cars       Family         15         16
  2000   Boats      Sport          20         21
  2000   Boats      Family         25         26
  ...
  </code></pre>
  
  <p>Dataset 2</p>
  
  <pre><code>Year   Category    ValueA     ValueB
  2000   Cars        100        101
  2000   Boats       200        201
  ...
  </code></pre>
  
  <p>Dataset 1 has its own crossfilter object, Dataset 2 has a separate crossfilter object. I have multiple dc.js charts, some tied to the dataset 1, some to dataset 2.</p>
  
  <p>When a dc.js chart filters dataset 1 on a column/dimension that also exists in dataset 2, I want to apply that same filter to dataset 2. How can this be achieved?</p>