If I'm honest, the most impressive thing about this is how much less concise this is than the mathematica version that came out earlier. I wonder if the difference is more a matter of the library quality or the syntax.
D3js is pretty verbose, but what you get is full control. Most charting libraries allow only a limited amount of configurability, which is neat if you just need to plot a basic chart quickly, but makes them awful if you want to make novel (or at least, more uncommon) kinds of visualisations or make non-standard changes to existing ones.
The best thing about this is that it doesn't require me to download and install 1.8 gigabytes of life-sucking Mathematica demo-version just to get a graph that I can draw on a napkin in 4 or 5 seconds ..
Well done! I actually was planning on tacking this one myself using svg filters but I've been too busy. I didn't see Mike Bostock's comment suggesting the custom line interpolator and wasn't aware of it -- d3 is gaining some cool new functionalities!
Thanks also for the great references. In spite of being a big proponent of d3, I somehow missed the "Toward Reusable Charts" piece Mike wrote earlier this year, which succeeds where I have struggled. I've been using the standard prototypal approach to creating reusable and easily configurable charts, which can be cumbersome for the caller. This functional approach with closures is so much cleaner and more reusable. It's the only way I'll make my d3 charts from now on!
Writing code makes repetitive tasks easier: if you want to pump out hundreds or thousands or millions of variations on a graph (using different data, etc...) then drawing it by hand is infeasible.
