  "How common is interactive visualization on the web?" "What is the most
popular visualization design?" "How prevalent are pie charts really?" These
questions intimate the role of interactive visualization in the real (online)
world. In this paper, we present our approach (and findings) to answering these
questions. First, we introduce Beagle, which mines the web for SVG-based
visualizations and automatically classifies them by type (i.e., bar, pie,
etc.). With Beagle, we extract over 41,000 visualizations across five different
tools and repositories, and classify them with 86% accuracy, across 24
visualization types. Given this visualization collection, we study usage across
tools. We find that most visualizations fall under four types: bar charts, line
charts, scatter charts, and geographic maps. Though controversial, pie charts
are relatively rare in practice. Our findings also indicate that users may
prefer tools that emphasize a succinct set of visualization types, and provide
diverse expert visualization examples.
