streamgraph.js by Jason Sundram.
From the post:
Streamgraphs are cool. They’re great at displaying trends in data over time, similar to a stacked graph, but much prettier. The first one I saw was Lee Byron’s Last.fm listening history graphic, a beautiful poster showing trends in the music he had listened to over the course of two years. The New York Times used an interactive streamgraph (created by Matthew Bloch and Shawn Carter) to great effect to show box office receipts over 22 years in The Ebb and Flow of Movies.
When Lee Byron & Martin Wattenberg open-sourced their streamgraph implementation in Java and Processing, I was pretty excited. I’ve been playing around with processing.js a lot lately, so I decided to port their code.
I’ve posted the code on github. The algorithms are much the same as Byron & Wattenberg’s, but I’ve added code to make the graphs more interactive and easily configurable.
Another visualization tool never hurt anyone.
And Jason says, these graphs are “prettier” than some alternatives. I will have to let someone else be the judge of the aesthetics but different visualizations work for different data sets and different people.