What you need to know
A line graph is used to compare two sets of data that are related in some way. Most commonly, a line graph is used to show how something changes over time – maybe over the course of a week, a year, or even longer.
Example: David collected data on how much sleep he got each night for a week. His results are collected in the table shown below. Construct a line graph to represent his data.
In this example, our line graph will be comparing how the amount of sleep David got changed over the course of a week. Typically, we choose to put the independent variable (i.e. the thing that we control) on the x-axis, whilst the dependent variable (the thing we’re measuring) goes on the y-axis. So, our line graph will have
• The days of the week on the x-axis, equally spaced;
• The number of hours of sleep on the y-axis.
Once you have drawn the axes, making sure both axes have been labelled, you should plot the points given in the table.
The result should look like the graph seen on the right.
Then, to make this into a line graph, we need to connect each of the individual points using straight lines. Finally, give your graph an appropriate title to describe what its showing, and the finished product looks like the graph shown below.
Our line graph should have the months on the x-axis and the temperature on the y-axis. It should also have the axes clearly labelled and an appropriate title at the top (don’t worry if yours is slightly different from my choice).
With all points plotted correctly and joined with straight lines, the line graph should look like:
The first mistake Roger made is that he didn’t label one of his axes.
The second mistake he made is that he plotted the 2014 point at 600 when it should be at 700.