Interactive Visual Exploration of Local Patterns in Large Scatterplot Spaces

Analysts often use visualisation techniques like a scatterplot matrix
(SPLOM) to explore multivariate datasets. The scatterplots of a SPLOM
can help to identify and compare two-dimensional global
patterns. However, local patterns which might only exist within
subsets of records are typically much harder to identify and may go
unnoticed among larger sets of plots in a SPLOM. This paper explores
the notion of local patterns and presents a novel approach to visually
select, search for, and compare local patterns in a multivariate
dataset. Model-based and shape-based pattern descriptors are used to
automatically compare local regions in scatterplots to assist in the
discovery of similar local patterns. Mechanisms are provided to
assess the level of similarity between local patterns and to rank
similar patterns effectively. Moreover, a relevance feedback module is
used to suggest potentially relevant local patterns to the user. The
approach has been implemented in an interactive tool and demonstrated
with two real-world datasets and use cases. It supports the discovery
of potentially useful information such as clusters, functional
dependencies between variables, and statistical relationships in
subsets of data records and dimensions.