Graphics Reference
In-Depth Information
F i g u r e . . Example of ordering glyphs according to one dimension. In this case, the data set is a subset
of the cars data, sorted by the MPG variable (top to bottom corresponds to low to high MPG). he
highlighted (dark) glyphs represent four-cylinder cars. A clear grouping of shapes is visible. A few
outliers can be seen near the bottom of the figure, which represent six-cylinder cars with good MPG
room for the user's focus region(s). his usually enables users to see subsets of the
data without the problem of occlusion. Distortion can also be used to enhance sep-
aration of subsets of data into groups. hus in an order-based layout, gaps between
adjacent glyphs can be set proportional to a similarity metric. In a sense, this can be
seen as a combination of structure and data-driven methods (Fig. . ).
Evaluation
7.8
Evaluation of the effectiveness of glyphs for information presentation and analysis
can be performed in a number of different ways. In this section, I describe several
such assessment processes, including:
Evaluation based on ranking of human perceptual abilities fordifferent graphical
attributes;
Evaluation based on the speed and accuracy of users performing specific tasks;
Evaluation basedoneaseofdetection ofdata features inthepresenceofocclusion
and clutter; and
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