title: pie chart from json using c3 js
body: <p>The code is taken as an example..</p>
  
  <p>I need to generate a pie chart having 4 divisions (site1,site2...)each division correspond to its respective upload value.</p>
  
  <p>In the above code i am not able to achieve this(I have specified value:['upload'])...</p>
  
  <p>what is the exact value i have to specify?</p>
  
  <p>Thanks..</p>
  
  <pre><code>  chart = c3.generate({
              data: {
                  json: [
                      {name: 'www.site1.com', upload: 200},
                      {name: 'www.site2.com', upload: 100},
                      {name: 'www.site3.com', upload: 300},
                      {name: 'www.site4.com', upload: 400},
                  ],
                  keys: {
      //                x: 'name', // it's possible to specify 'x' when category axis
                      value: ['upload'],
                  },
                  type:'pie'
              },
              axis: {
                  x: {
      //                type: 'category'
                  }
              }
          });
  </code></pre>