Definitions
Figure 2 provides a visual reference for the
following definitions.
Indicators. Indicators are the elements in a
graph that express the value of the dependent
variable for a given value or category of an
independent variable. Examples include the
plotting symbols and lines in a line graph, bars
in a bar graph, pie segments in a pie chart,
and plotting points in a scatter plot.
Axes. The y axis is a vertical line at the left
edge of the graph (and sometimes is repeated
at the right edge). The x axis is a horizontal
line at the bottom of the graph.
Labels. Verbal labels are used for variable
names on the x and y axes. In addition, verbal
labels can be used to name levels of a categorical
independent variable. In a graph that contains
only one independent variable, the levels
would be represented as specific points on the
x axis corresponding to bars in a bar graph or
points in a line graph. In a figure that contains
multiple independent variables, the levels of
one categorical independent variable might be
represented as separate lines in a line graph or
as separate graphs; each level should have a
unique label.
Quantitative labels include the scale values
associated with the axes. Quantitative labels
may also be used to provide values for levels
of an independent variable.
Background. The background includes any
graphical marks falling within the axes in addition
to the indicators. In scientific graphs, one
common background is an extension of the
tick marks from one or both axes, forming a
grid that appears to be behind the indicators.