Basser Seminar Series

Dimensionality Reduction From Several Angles

Speaker: Professor Tamara Munzner
University of British Columbia, Canada

When: Tuesday 9 June 2015, 12:00-1:00pm. Please note different day and time to usual.

Where: The University of Sydney, School of IT Building, SIT Lecture Theatre (Room 123), Level 1

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Abstract

I will present several projects that attack the problem of dimensionality reduction (DR) in visualization. Much of this work was informed by a two-year qualitative study of high-dimensional data analysts in many domains, to encapsulate the use of DR "in the wild" as a small set of abstract tasks. We used different methodological angles of attack in order to answer different kinds of questions, according to our Nested Model of visualization design and evaluation. First, can we design better DR algorithms? Glimmer is a multilevel multidimensional scaling (MDS) algorithm that exploits the GPU. Glint is a new MDS framework that achieves high performance on costly distance functions. Second, can we build a DR system for real people? DimStiller is a toolkit for DR that provides local and global guidance to users who may not be experts in the mathematics of high-dimensional data analysis, in hopes of "DR for the rest of us". Third, how should we show people DR results? An empirical lab study provides guidance on visual encoding for system developers, showing that points are more effective than spatialized landscapes for visual search tasks with DR data. A data study, where a small number of people make judgements about a large number of datasets rather than vice versa as with a typical user study, produced a taxonomy of visual cluster separation factors. Fourth, when do people need to use DR? Sometimes it is not the right solution, as we found when grappling with the design of the QuestVis system for a environmental sustainability simulation. We provide guidance for researchers and practitioners engaged in this kind of problem-driven visualization work with a nine-stage framework for Design Study Methodology.

Speaker's biography

Tamara Munzner is a professor at the University of British Columbia Department of Computer Science, and holds a PhD from Stanford. She has been active in visualization research since 1991 and has published over sixty papers and book chapters. Her book Visualization Analysis and Design appeared in 2014. She co-chaired InfoVis in 2003 and 2004, co-chaired EuroVis in 2009 and 2010, and is chair of the InfoVis Steering Committee and the VIS Executive Committee. Her research interests include the development, evaluation, and characterization of information visualization systems and techniques. She has worked on problem-driven visualization in a broad range of application domains, including genomics, evolutionary biology, geometric topology, computational linguistics, large-scale system administration, web log analysis, and journalism. Her technique-driven interests include graph drawing and dimensionality reduction. Her evaluation interests include both controlled experiments in a laboratory setting and qualitative studies in the field.