Database Reference
In-Depth Information
uu A line chart traces a value continuously over time, but unlike a timeline, it
varies its position vertically. Choosing between a line chart and the other
charts is easy; if the values can be interpolated over time, such as a rise in
temperature throughout a day, then a line chart is appropriate. If values
cannot be interpolated—for example the chart is showing the seven days
of the week, and the data has sales for only three of those days—connect-
ing those points is inappropriate and misleading.
uu A bar chart , with bars positioned vertically above each other, is a useful
tool for showing discrete values that start and end at different dates. In
the case of a bar chart, positioning on the vertical axis is a point in a series
rather than an additive value. Graphically, a bar chart resembles a timeline
in that it has a graphical element stretching between two points. If these
points are on an axis of dates, the bar chart is a timeline.
uu A column chart , in which columns are positioned horizontally next to each
other, is useful for showing values where the addition of the individual
values would be meaningful. An example is a chart for sales value, with
each column representing the value of sales for a given time period, such
as a financial month.
uu A combined chart combines column and line charts, typically for showing
percentages or trends.
uu A point or scatter plot is useful for discrete values in which the addition, or
“summing,” of the individual values would make little sense. This type of
chart is often used in scientific research or for the results of opinion polls.
Additional data can be added to a chart of this type by changing the size
of the point; this is called a bubble chart. (Bubble charts are the most com-
monly animated chart type, as showing a bubble growing and shrinking
over time illustrates the changes over time very effectively—temporal
analysis is one of the places where animation works well).
uu Tiling —repeating the same chart, either horizontally or vertically, with
each repetition showing a different point in time—is a way of increasing
the available dimensions to show other values. Because both x- and y-axes
are now available for non-time dimensions, the information available in
a single chart increases at the expense of screen space and the size of
each individual chart.
uu Animations are the latest addition to temporal analysis. Showing changes
in time by animating is an easy way to add an extra dimension to analy-
sis without consuming additional space. Most typically combined with
scatter plots, other ways of showing changes over time are also possible.
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