What is a Line Graph?
Support Page

A good example of a line graph showing the distance travelled during a cycle ride

So why is this a GOOD example?

The data points show the distance Frazer traveled during a cycle ride with measurments taken at 15 minute intervals.

In this line graph the inbetween, or intermediate, points do have meaning.

If we look at any point on the line graph then that point shows roughly how far Frazer has traveled at a given amount of time.

The data works well as a line graph because it is continuous and the inbetween points show the time and approximate distance traveled.

A bad choice of a line graph showing different tree heights

So why is this a BAD example?

The data points show the average heights of different trees.

In a line graph the inbetween, or intermediate, points should ideally have some meaning or help to show a trend.

If we look at a point on the line halfway between any two trees, such as the Australian Mountain Ash and the Coast Douglas Fir, the point has no meaning at all and does not show any kind of trend.

There is no trend to see because the trees are all a completely different species.

The data this line graph is showing is NOT continuous and there is no reason to connect the different trees together with a line.

This data would be much better displayed as a bar graph like the one below.

Example 1) Line Graph showing the distance traveled during a cycle ride

Let's have another look at this line graph and see what the line is telling us..

We can see that in the first hour (60 minutes) Frazer cycled 12 miles.

We can see that between 75 and 90 minutes Frazer did not travel any further, so he must have had a rest, or stopped to fix a flat tyre.

In the second hour, between 60 and 120 minutes, Frazer only managed to travel a further 8 miles.

If we were asked to estimate how far he had cycled in the first 20 minutes, we can use the line to say that he had traveled about 4 miles.

Example 2) Line Graph showing a survey of the number of Galapagos Penguins.

The line graph above, shows the number of Galapagos penguins seen during a penguin survey each year.

Looking at the line graph, we can see:

• The number of Galapagos penguins was at the lowest in 2011. Only 25 penguins were seen.
• The steepest decrease in population was between 2008 and 2009.
• Between 2009 and 2010, the number of Galapagos penguins seen remained unchanged.
• The steepest increase in population was between 2015 and 2016.

Example 3) Line Graph showing the average price of a gold ounce from 2013 to 2023.

The line above shows the average gold price per ounce from 2013 to 2023 rounded to the nearest $20.

Looking at the graph, we can see:

• The average price decreased between 2013 and 2015.
• After 2015, the average price has been in an upward trend and has increased most years.
• Between 2016 and 2018, and also between 2020 and 2022, the price stayed flat and did not change much.
• The sharpest increase was between 2019 and 2020.