title: d3 Filtering data
body: <p>I have the csv file</p>
  
  <pre><code>Crime Category Description, Crime Code, Month Of Arrest
  NONE, 123, 1
  NONE, 234, 4
  THEFT, 333, 4
  THEFT, 444, 3
  BATTERY, 456, 5
  BATTERY, 55, 3
  </code></pre>
  
  <p>I try to filter the data where "Crime Category Description" = "THEFT" and
  "Crime Category Description" = "BATTERY".
  To do this, I use </p>
  
  <pre><code>d3.csv("Urbana_Police_Arrests_Since_1988.csv", function(error,data){
  ...
  .enter().append("rect")
  .data(data.filter(function(d){return d.key = "THEFT" &amp;&amp; d.key == "BATTERY" }))
  </code></pre>
  
  <p>Unfortunately, it does not work. Any ideea why?</p>
  
  <p>Output should be:</p>
  
  <pre><code>THEFT, 333, 4
  THEFT, 444, 3
  BATTERY, 456, 5
  BATTERY, 55, 3
  </code></pre>