Scalable Visual Comparison of Biological Trees and Sequences

We present the TreeJuxtaposer and SequenceJuxtaposer visualization applications for comparing and browsing evolutionary trees and genomic sequences, respectively. These systems use the Focus+Context navigational metaphor of allowing users to fluidly stretch and shrink parts of the view, as if manipulating a rubber sheet with the borders tacked down. We introduce cognitive scalability to this approach by guaranteeing the visibility of landmarks at all times, so that users can stay oriented as they explore complex datasets. In our systems, landmarks can be regions of difference between datasets, or the results of a search, or user-chosen regions. This technique, which we call "accordion drawing," supports smooth realtime transitions between a big-picture overview and a drilled-down views that show details in context. Our new PRISAD infrastructure is highly scalable, allowing fluid realtime interaction with trees of several million nodes and multiple aligned sequences of up to 40 million total nucleotides.