title: D3: how to create a bar chart by row with a csv file
body: <p>I just started playing around with D3 and created my first bar chart using a .CSV file.</p>
  
  <p>The csv file looked as follow:</p>
  
  <pre><code>"browser","marketshare"
  "firefox", 20
  "IE", 45
  "Chrome", 30
  "opera", 5
  </code></pre>
  
  <p>using the following code for my rectangles would result in 4 rectangles with the height of 20, 45, 30, 5</p>
  
  <pre><code>.attr("height", function(d) { return d.marketshare; });
  </code></pre>
  
  <p>now I have a slightly different file </p>
  
  <pre><code>"browser","2001","2002","2003","2004"
  "firefox",20,19,22,25
  "IE", 45,40,39,35
  "Chrome", 30,33,35,37
  "opera", 5,4,5,4
  </code></pre>
  
  <p>What I'd like to do is create 5 separate bar charts one for firefox, IE, Chrome and opera.
  Let's say I want to create one for firefox. How can I change: function(d), so that it will create rectanlges for the year 2001, 2002, 2003, 2004 and that only for firefox. </p>
  
  <p>Any help is greatly appreciated</p>
  
  <p>Thanks in advance!</p>