The wood and the trees - The Visualization of Spatial Social Structure - page 237

Box 8.3 Constructing face glyphs

The face glyphs used in this topic are a
modern and somewhat less ambitious
development of those originally cre-
ated by Chernoff (1973). Here, only
five variables are shown and the faces
are made to look somewhat more life-
like through the use of curves, rather
than lines, to describe them. The faces
are each described by a single path
made up of eleven Bezier curves, each
consisting of two control points and
an absolute point (which the curve
must lie on). Three curves are used
to describe the shape of the face and
two each for the eyes, nose and mouth.
The control points are shown, shaded
in grey, behind the faces.
The minimum, maximum and
average extent of each curve is shown.
The absolute points remain fixed, ensuring that the general character of the
shape does not alter too much and that features will not overlap. The faces
used here are symmetrical, as that produced the most pleasing results. After
shape, eye size, nose size and smile, the overall size of the face allows up
to five variables to be presented at once, in a very novel manner. See code
in Appendix to this volume.

Lowest
Levels

Average Levels

Highest
Levels

best equipped and experienced to decipher. We naturally combine their features
to interpret moods - such as happy or sad, or sly. What is more, we can easily
compare faces to look for family resemblances or the mood of the crowd. 12 Faces
maintain a basic structure in which even slight variation often holds meaning.
The original Chernoff faces aimed to show the values of as many as eighteen
variables simultaneously. Here the aim is somewhat less ambitious (Box 8.3
and Figure 8.7). Chernoff faces have been used here to study general election

12 Possibly the first suggestion of drawing crowds, or at least not objecting to such a drawing on a
cartogram was made here: ' ... engineers prefer line graphs, sales people bar charts, demographers pie
charts and medical personnel lists of numbers. Epidemiologists, at least those dealing with cancers,
seem to appreciate horizontal bars. In cancer statistics and epidemiology the discrepancy between
sophisticated statistical methodology and elementary graphical techniques is large. Certainly, elegant
technical refinements can be found in cancer mapping, but even here there is exciting potential
for maximizing the information content of maps by combining cancer frequency levels with, e.g.,
indices of data quality. Moreover, no objections exist to combining cartograms and faces' (Rahu,
1989, p. 765).