Matthew O. Ward
Computer Science Department
Worcester Polytechnic Institute
Worcester, MA 01609 USA
Abstract - Glyphs (also referred to as icons) are graphical entities which convey one or more data values via attributes such as shape, size, color, and position. They have been widely used in the visualization of data and information, and are especially well suited for displaying complex, multivariate data sets. The placement or layout of glyphs on a display can communicate significant information regarding the data values themselves as well as relationships between data points, and a wide assortment of placement strategies have been developed to date. Methods range from simply using data dimensions as positional attributes to basing placement on implicit or explicit structure within the data set. This paper presents an overview of multivariate glyphs, a list of issues regarding the layout of glyphs, and a comprehensive taxonomy of placement strategies to assist the visualization designer in selecting the technique most suitable to his or her data and task. Examples, strengths, weaknesses, and design considerations are given for each category of technique, and relations are drawn to other disciplines where placement of symbols has significance, such as VLSI design and cartography.
Index Terms - Multivariate data visualization, glyphs, layout algorithms.