Drawing plots with NVD3

D3 is a library that offers low-level components for building interactive visualizations in JavaScript. By offering the low-level components, it gives a huge degree of flexibility to the developer. The learning curve can, however, be quite steep. In this example, we will use NVD3, a library which provides pre-made graphs for D3. This can greatly speed up initial development. We will place the code in the file repoGraph.js and expose a single method, build, which takes, as arguments, a model and a div and draws a pie chart in that div. The pie chart will aggregate language use across all the user's repositories.

The code for generating a pie chart is nearly identical to the example given in the NVD3 documentation, available at http://nvd3.org/examples/pie.html. The data passed to the graph must be available as an array of objects. Each object must contain a label field and a size field. The label field identifies the language, and the size field is the total size...