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Pie charts

Pie charts show percentages as a circle, divided into segments. A pie chart could be used to show how students travel to school. Each piece of data is shown as a proportion of 360, because there are 360 degrees in a circle. If 25 out of 100 students travel to school by car, the angle is worked out using the calculation: (25 ÷ 100) × 360 = 90 degrees.

Transects and kite diagrams

A transect is a line across a habitat or part of a habitat. It can be as simple as a string or rope placed in a line on the ground. The number of organisms of each species can be observed and recorded at regular intervals along the transect.

A kite diagram is a graph that shows the number of animals (or percentage cover for plants) against distance along a transect.

Hydrographs

A hydrograph shows two graphs - rainfall (in bars) and discharge (in a line).

Interpreting a hydrograph

The peak rainfall is the time of highest rainfall. The peak discharge (the time when the river reaches its highest flow) is later because it takes time for the water to find its way to the river (lag time). The normal (base) flow of the river starts to rise (rising limb) when run-off, ground and soil water reaches the river. Rock type, vegetation, slope and situation (for example, is this an urban river?) affect the steepness of this limb. The falling limb shows that water is still reaching the river but in decreasing amounts. The run-off/discharge of the river is measured in cumecs - this stands for cubic metres per second. Precipitation is measured in mm - this stands for millimetres.

Scatter graphs

Scatter graphs show relationships between two sets of data. Points are located using the x and y-axis. Sometimes these points are arranged in a pattern. A scatter graph could be used to show how literacy is related to gross domestic product (GDP).

A line of best fit helps to show correlations, or patterns within the data. The line of best fit runs through the middle of points on the graph, ideally with an equal number of points on either side of the line.

• A strong correlation is when the points are very close to the line of best fit.
• A weak correlation is when the points are far away from the line of best fit.
• A positive correlation is when an increase in one factor causes an increase in another - the line of best fit goes from the bottom left to the top right.
• A negative correlation is when an increase in one factor causes a decrease in another - the line of best fit goes from the top left to the bottom right.

Proportional symbols, pictograms and cross-sections

Proportional symbols can be added to maps or graphs to show information about different places. This graph plots life expectancy against income for each country. It also shows population size. Each country is shown as a circle, where the size of the circle is proportional to the population of the country, ie the bigger the circle, the bigger the population of that country.

Pictograms are like bar charts, but they use small pictures or icons to show data instead of bars. Pictograms could be used to show the weather conditions experienced in a particular place.

Cross-sections are line graphs that show a sideways view of a landscape. They can show features such as hills and valleys, or depths, such as the depth of a river. Cross-sections of hills use contour lines to determine the height of the land. Cross-sections of river depths are drawn using negative numbers so that the line graph looks like depth, rather than height.

Radial/radar graphs

Radial/radar graphs are sometimes called rose charts. They have a central point from which data radiates outwards. This data can be plotted as points along a line, where all points are joined up to form a shape. It could also be plotted as segments along a line. Wind speed and direction is often shown as a radial graph. Radial graphs can show lots of different data and do not have to involve compass points.