Information Technology Reference
In-Depth Information
we illustrate five important rules for generating correct graphics. Subse-
quent sections will augment this list with other specific examples.
Figure 8.1 includes a false third dimension; a depth dimension that does
not correspond to any information in the data. Furthermore, the resulting
figure makes it difficult to discern the actual values presented. Can you tell
by looking at Figure 8.1 that Team 3 scored 14 goals, or does it appear
that they scored 13 goals? The reader must focus on the top back corner
of the three-dimensional rectangle since that part of the three-dimensional
bar is (almost) at the same level as the grid lines on the plot; actually, the
reader must first focus on the floor of the plot to initially discern the verti-
cal distance of the back right corner of the rectangular bar from the corre-
sponding grid line at the back (these are at the same height). The viewer
must then mentally transfer this difference to the top of the rectangular
bars in order to accurately infer the correct value. The reality is that most
people focus on the front face of the rectangle and will subsequently mis-
interpret this data representation.
Figure 8.2 also includes a false third dimension. As before, the resulting
illustration makes it difficult to discern the actual values presented. This
illusion is further complicated by the fact that the depth dimension has
been eliminated at the top of the three-dimensional pyramids so that it's
nearly impossible to correctly ascertain the plotted values. Focus on the
result of Team 4, compare it to the illustration in Figure 8.1, and judge
whether you think the plots are using the same data (they are). Other
types of plots that confuse the audience with false third dimensions
include point plots with shadows and line plots where the data are con-
nected with a three dimensional line or ribbon.
The lesson from these first two graphics is that we must avoid illustra-
tions that utilize more dimensions than exist in the data. Clearly, a better
presentation would indicate only two dimensions where one dimension
identifies the teams and the other dimension identifies the number of
goals scored.
Rule 1: Don't produce graphics illustrating more dimensions
than exist in the data.
Figure 8.3 is an improvement over three-dimensional displays. It is
easier to discern the outcomes for the teams, but the axis label obscures
the outcome of Team 4. Axes should be moved outside of the plotting
area with enough labels so that the reader can quickly scan the illustration
and identify values.
Rule 2: Don't superimpose labeling information on the graphical
elements of interest. Labels can add information to the plot, but
Search WWH ::




Custom Search