By Luke Francl (look@recursion.org), August 2011 d3.js is a data visualization library by Mike Bostock, who is also the primary creator of Protovis, which D3 is designed to replace. D3 has a steep learning curve, especially if (like me) you are not used to the pixel-precision of graphics programming. To build a visualization with D3, you need to understand JavaScript objects, functions, and the me