Database Reference
In-Depth Information
Similarly, visualizing multiple trends over time creates a visual cue to related
trends or contra-related trends. Seeing a correlation between an increase in
profits related to a decrease in customer satisfaction might indicate a cost-
saving measure that has affected product quality, and visualizations showing
these changes over time aid in sparking that intuitive leap.
Traditionally, temporal analysis has been used by historians and in the medical
field to track the progress of diseases both in individuals and in the popula-
tion at large. In business, the biggest users of timelines have been in sales and
finance departments where they track sales and profitability against costs.
TyPeS oF TeMPoRAl AnAlySIS
VISuAlIzATIon
How you illustrate a change over time is primarily dependent on whether you
have to do so in a static manner or whether you can create an animated visu-
alization. Many early examples of showing a time change in the film industry
used an animation of calendar pages being torn of a calendar, which is a great
example of illustrating the passage of time, but it doesn't show any other data
points. To show data points against the passage of time on a static medium
(such as a printed chart, or indeed in a chart on a computer screen), one of
the dimensions of the chart needs to be chosen to represent the passage of
time. The convention is that this is done left to right. There are certain types
of visualizations that use top to bottom (or even bottom to top); if you use
one of these formats then include an indicator that helps the reader of the
chart know that you have used an unconventional format.
Charts that use the horizontal axis to show position in time use the vertical
axis to show the value of a data point. A data point can be represented as a
point, a column, a line, or a bar.
The other ways of showing changes over time are animation and tiling—i.e.,
repeating a chart over a time axis. The following list introduces each of the
chart types described later in this chapter:
uu
A
timeline
is the earliest form of temporal chart. It shows a change over
time, generally from left to right, but sometimes also from top to bottom.
The length of the line indicates the amount of time, as well as the start
and end dates.
