Line Graph

A line graph, also known as a line chart, is a type of chart used to visualize the value of something over time. For example, a finance department may plot the change in the amount of cash the company has on hand over time.

The line graph consists of a horizontal x-axis and a vertical y-axis. Most line graphs only deal with positive number values, so these axes typically intersect near the bottom of the y-axis and the left end of the x-axis. The point at which the axes intersect is always (0, 0). Each axis is labeled with a data type. For example, the x-axis could be days, weeks, quarters, or years, while the y-axis shows revenue in dollars.

Data points are plotted and connected by a line in a "dot-to-dot" fashion.

The x-axis is also called the independent axis because its values do not depend on anything. For example, time is always placed on the x-axis since it continues to move forward regardless of anything else. The y-axis is also called the dependent axis because its values depend on those of the x-axis: at this time, the company had this much money. The result is that the line of the graph always progresses in a horizontal fashion and each x value only has one y value (the company cannot have two amounts of money at the same time).

More than one line may be plotted in the same axis as a form of comparison. For example, you could create a line graph comparing the amount of money held by each branch office with a separate line for each office. In this case each line would have a different color, identified in a legend.

Line graph example

The line graph is a powerful visual tool for marketing, finance, and other areas. It is also useful in laboratory research, weather monitoring, or any other function involving a correlation between two numerical values. If two or more lines are on the chart, it can be used as a comparison between them.

Line chart

How to Create a Line Graph

  • Create a table. Draw the x- and y-axes on the page. On the top of the page, place a title that briefly describes the purpose of the chart.
  • Label each axis. If time is one of the factors, it should go along the horizontal (x) axis. The other numeric values measured should be placed along the vertical (y) axis. Each axis should be labeled with the name of the numeric system as well as the measurements being used. For example, you may label the x axis with "Time (Days)", indicating that each number written on the axis is a number of days. Divide each axis evenly into applicable increments.
  • Add data. Data for a line graph is usually contained in a two-column table corresponding to the x- and y-axes. With SmartDraw you can also import data from Excel. Once you've added your data, your line graph will automatically reflect its values. If you want to call attention to any particular value, you can add a label with an arrow pointing to it.
  • Create a key. If you are comparing multiple items, you'll want to create a key that identifies what each line is by its color.