A graph is a pictorial representation of the relationship between two
or more physical quantities. Graphs are used frequently both to
present fundamental data on the behavior of physical systems and to
monitor the operation of such systems. The basic principle of any
graph is that distances are used to represent the magnitudes of
numbers. The number line is the simplest type of graph. Below is an
example of a number line graph.
All numbers are represented as distances along the line. Positive
numbers are located to the right of zero, and negative numbers are
located to the left of zero.
The coordinate system of a graph is the framework upon which the
graph is drawn. A coordinate system consists of numbered scales that
give the base and the direction for measuring points on the graph. Any
point on a graph can be specified by giving its coordinates.
Coordinates describe the location of the point with respect to the
scales of the coordinate system. There are several different
coordinate systems that all students must learn and understand how to