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• There are a variety of different types of graphs that can be used to show geographical data.
• Graphs can be used to show patterns.
• Graphs can be used to help reach conclusions.

In geography it is important to be able to read and understand data that is presented in a range of different ways. We often use graphs to present data in a clear and accessible way. There are many different types of graphs but those used most frequently in geography are described below.

Line graphs are used to show continuous changes over time. A line graph might be useful for showing the pattern of change in world population, for example.

The line graph below shows the population growth of low income, middle income, and high income countries between 1960 and 2020.

Scatter graphs show how two sets of data are related to each other. Data points are plotted on a graph and then a line of best fit is drawn to show the overall trend, if there is one. The trend is usually described as a correlation. When the line of best fit has a positive gradient, there is positive correlation. If the line of best fit has a negative gradient, there is a negative correlation.

Bar charts are used to compare different categories. The bars must be separated by gaps because the categories are unconnected.

The bar chart below shows different types of vehicle that were seen during a traffic survey.

Histograms look similar to bar charts as they both display data using bars. A histogram shows continuous data, such as different age groups, and therefore the bars are drawn without gaps between them.

The population pyramid below shows the age range of people in Japan's population.

Pie charts are represented as a circle divided into segments. A full pie chart represents 100% and each slice, or segment, shows what proportion that category is of the whole.

The pie chart below shows the estimated population of Europe in 2021. Each segment of the chart represents a different age range, showing what percentage of the population is in each age group.

Sometimes, graphs may be combined together. For example, a climate graph and a flood hydrograph both present data using a bar chart and a line graph in a single graph.

Although these graphs can appear complicated, focus on the three boxes at the top - peak rainfall, lag time and peak discharge. The graph is showing how long it takes rainfall water to reach the rivers.

When examining data on a graph, there are certain things to look for, such as the overall trend, the rate of change, and any anomalies. When describing what a graph shows, it is best to deal with each of these in turn.

Step 1 - describe the overall trend.

Eg: The population is increasing.

Step 2 - describe the rate of change.

Eg: The increase has been rapid.

Step 3 - point out any data points that don't fit the overall pattern. These are called anomalies.

Eg: The increase was rapid, apart from in 2008 when it slowed.

Step 4 - include some figures as evidence.

Eg: The increase was rapid, changing from 1 billion in 1800 to 7 billion in 2011.

Interpreting a graph means to explain why it shows what it does. It may be that the population of a country has increased because of improvements in health care, for example. You should consider why anomalies exist. For example, a war may cause a fall in population.