protovis javascript charts: part 1

Finally lets make a pie chart. In Protovis, this is called a Wedge so replace Dot with the word Wedge.

Wedge has a few important differences. Data in a pie chart illustrates the proportion of the whole, or more simply put the percentage. Protovis gives us several simple ways to calculate this. In this case, we're going to use a method called pv.normalize. This makes the sum of the data equal to one and creates a copy of the array. Remember 1 is just 2 decimal places away from 100 so this effectively creates a new array with percentage values and passes it down the chain.

Next we need to center the Wedge chart. We do this by setting left and bottom to 75.

Set the outerRadius to 70 pixels to leave 5 pixels of space around the chart. A wedge appears in the Web preview window.