Visualization of large amounts of multidimensional multivariate business-oriented data

Abstract

Many large businesses store large amounts of business-oriented data in data warehouses. These data warehouses contain fact tables, which themselves contain rows representing business events, such as an individual sale or delivery. This data contains multiple dimensions (independent variables that are categorical) and very often also contains multiple measures (dépendent variables that are usually continuous), which makes it complex for casual business users to analyze and visualize. We propose two techniques, GPLOM and VisReduce, that respectively handle the visualization front-end of complex datasets and the back-end processing necessary to visualize large datasets. Scatterplot matrices (SPLOMs), parallel coordinates, and glyphs can all be used to visualize the multiple measures in multidimensional multivariate data. However, these techniques are not well suited to visualizing many dimensions. To visualize multiple dimensions, “hierarchical axes” that “stack dimensions” have been used in systems like Polaris and Tableau. However, this approach does not scale well beyond a small number of dimensions. Emerson et al. (2013) extend the matrix paradigm of the SPLOM to simultaneously visualize several categorical and continuous variables, displaying many kinds of charts in the matrix depending on the kinds of variables involved. We propose a variant of their technique, called the Generalized Plot Matrix (GPLOM). The GPLOM restricts Emerson et al. (2013)’s technique to only three kinds of charts (scatterplots for pairs of continuous variables, heatmaps for pairs of categorical variables, and barcharts for pairings of categorical and continuous variable), in an effort to make it easier to understand by casual business users. At the same time, the GPLOM extends Emerson et al. (2013)’s work by demonstrating interactive techniques suited to the matrix of charts. We discuss the visual design and interactive features of our GPLOM prototype, including a textual search feature allowing users to quickly locate values or variables by name. We also present a user study that compared performance with Tableau and our GPLOM prototype, that found that GPLOM is significantly faster in certain cases, and not significantly slower in other cases. Also, performance and responsiveness of visual analytics systems for exploratory data analysis of large datasets has been a long standing problem, which GPLOM also encounters. We propose a method called VisReduce that incrementally computes visualizations in a distributed fashion by combining a modified MapReduce-style algorithm with a compressed columnar data store, resulting in significant improvements in performance and responsiveness for constructing commonly encountered information visualizations, e.g., bar charts, scatterplots, heat maps, cartograms and parallel coordinate plots. We compare our method with one that queries three other readily available database and data warehouse systems — PostgreSQL, Cloudera Impala and the MapReduce-based Apache Hive — in order to build visualizations. We show that VisReduce’s end-to-end approach allows for greater speed and guaranteed end-user responsiveness, even in the face of large, long-running queries.

Date	24 Nov 2014
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Michael John McGuffin (Supervisor)