Information Technology Reference
In-Depth Information
symbols with associated labels if such replacement results in a readable
(nonoverlapping) presentation. If our focus highlights a few key points, we
can substitute labels for only those values.
When replacing (or decorating) symbols with labels results in an over-
lapping indecipherable display, a legend is an effective tool provided that
there are not too many legend entries. Producing a graphical legend with
100 entries is not an effective design. It is an easy task to design these ele-
ments when we stop to consider the purpose of the graphic. It is wise to
consider two separate graphics when the amount of information over-
whelms our ability to document elements in legends and the caption.
Too many line styles or plotting points can be visually confusing and
prevent inference on the part of the reader. You are better off splitting the
single graphic into multiple presentations when there are too many sub-
groups. An ad hoc rule of thumb is to limit the number of colors or
symbols to less than eight.
Rule 10:
Keep line styles, colors, and symbols to a minimum.
MULTIDIMENSIONAL DISPLAYS
Representing several distinct measures for a collection of points is prob-
lematic in both text and graphics. The construction of tables for this
display is difficult due to the necessity of effectively communicating the
array of subtabular information. The same is true in graphical displays, but
the distinction of the various quantities is somewhat easier.
CHOOSING EFFECTIVE DISPLAY ELEMENTS
As Cleveland and McGill (1988) emphasize, graphics involve both encod-
ing of information by the graphic designer and decoding of the informa-
tion by the reader. Various psychological properties affect the decoding of
the information in terms of the reader's graphical perception. For example,
when two or more elements are presented, the reader will also envision
byproducts such as implied texture and shading. These byproducts can be
distracting and even misleading.
Graphical displays represent a choice on the part of the designer in terms
of the quantitative information that is highlighted. These decisions are
based on the desire to assist the analyst and reader in discerning perfor-
mance and properties of the data and associated models fitted to the data.
While many of the decisions in graphical construction simply follow con-
vention, the designer is still free to choose geometric shapes to represent
points, color or style for lines, and shading or textures to represent areas.
The referenced authors included a helpful study in which various graphical
styles were presented to readers. The ability to discern the underlying infor-
