Glyph Fundamentals

Multivariate data (also called multidimensional or n-dimensional) consists of some number of points, m, each of which is defined by an n-vector of values.

Such data can be viewed as an mxn matrix, where each row represents a data point and each column represents an observation (also called a variable or dimension).

An observation may be nominal or ordinal, and may or may not have a distance metric, ordering relation, or absolute zero.

Each variable/dimension may be independent or dependent.

A glyph consists of a graphical entity with p components, each of which may have r geometric attributes and s appearance attributes.

Typical geometric attributes include shape, size, orientation, position, and direction/magnitude of motion, while appearance attributes include color, texture, and transparency.

Attributes can be discrete or continuous, scalar or vector, and may or may not have a distance metric, ordering relation, or absolute zero.

The list below (and Figure) give examples of glyphs from the literature and attributes controlled by the multivariate data point.

  

Figure 1: Examples of glyphs: variations on profiles; stars/metroglyphs; stick figure icons and trees; autoglyphs and boxes; faces; arrows and weathervanes.

• profiles [17]: height and color of bars.
• stars [45]: length of evenly spaced rays emanating from center.
• Anderson/metroglyphs [1,20]: length of rays.
• stick figure icons [39]: length, angle, color of limbs.
• trees [29]: length, thickness, angles of branches; branch structure derived from analyzing relations between dimensions.
• autoglyph [4]: color of boxes.
• boxes [21]: height, width, depth of first box; height of successive boxes.
• faces [6]: size and position of eyes, nose, mouth; curvature of mouth; angle of eyebrows.
• arrows[48]: length, width, taper, and color of base and head.
• weathervanes [18]: level in bulb, length of flags.
• circular profiles [37]: distance from center to vertices at equal angles.
• bugs [9]: wing shapes controlled by time series; length of head spikes (antennae); size and color of tail; size of body markings.
• wheels [9]: time wheels create ring of time series plots, value controls distance from base ring; 3D wheel maps time to height, variable value to radius.
• Glyphmaker [40]: user-controlled mappings.