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A line graph is used to show how a set of data changes with respect to another quantity, often a period of time. To make a line graph, a scale and intervals for the coordinate axes are chosen. The data points are then graphed and a line connecting the points drawn. Consider a table of values that represents the growth of a plant over several weeks.
| Plant Growth | |||||
|---|---|---|---|---|---|
| Week | 1 | 2 | 3 | 4 | 5 |
| Height (in.) | 1.5 | 2.3 | 4 | 6.2 | 8 |
The height data includes values from 1.5 to 8, so a scale from 0 to 10 inches with an interval of 1 inch is reasonable. The horizontal axis can represent time in weeks and the vertical axis can represent the plant height in inches. Now the points can be plotted on a coordinate plane and connected with a line.
By observing the upward and downward slant of the lines connecting the points, the trends in the data can be described and future events can be predicted.