Graphs & Diagrams (Cambridge (CIE) IGCSE Geography)

Graphs & Diagrams

Types of data

• Continuous data is numerical data that can take any value within a given range, e.g. heights and weights

• Discrete data is numerical data that can only take certain values, e.g. shoe size

• Quantitative data is where the results can be expressed using numerical values

• Qualitative data is where the results can’t be expressed as numbers, e.g. opinions

Line graph

• One of the simplest ways to display continuous data

• Both axes are numerical and continuous

• Used to show changes over time and space

Example

• A river cross-section is a particular form of line graph because it is not continuous data, but the plots can be joined to show the shape of the river channel

Bar chart

• A bar chart is the simplest form of displaying data

• Each bar is the same width but can have varying lengths

• Each bar is drawn an equal distance apart (equidistant)

• The data is discrete data

• Bar graphs are useful for:

  • Comparing classes or groups of data

  • Changes over time

Example

Histograms

• Histograms show continuous data

• Always use a ruler to draw the bars

• All bars should be the same width 

• The top of the bar should reach the number on the side of the graph that is being represented

• There should be no gaps; all bars should be touching

• Ensure all axes are labelled and that the graph has a title

Example

Compound or divided bar chart

• The bars are subdivided to show the information, with all bars totalling 100%

• Divided bar charts show a variety of categories

• They can show percentages and frequencies

Example

Population pyramid

• This is a type of histogram

• Used to show the age-sex of a population

• It can be used to show the structure of an area/country

• Patterns are easy to identify

Example

Pie chart

• Used to show proportions, the area of the circle segment represents the proportion

• A pie chart can also be drawn as a proportional circle 

• Pie charts can be located on maps to show variations at different sample sites

• The percentage of the pie chart must add up to 100%

• To calculate degrees of the pie chart (which totals 360°), divide the percentage by 100 and then multiply by 360

• Each segment should be a different colour

Example

Rose diagram

• Uses multidirectional axes to plot data with bars

• Compass points are used for the axis's direction

• Can be used for data such as wind direction, noise or light levels

Example

Triangular graph

• Triangular graphs are used to display data, which can be divided into three

Example

• Read each side carefully so you are aware which direction the data should be considered

  • Always read from 0 to 100 and follow through to the next 0

  • Can be either clockwise or counter-clockwise

  • In the example below, the data reads clockwise

Scatter graph

• Points should not be connected

• The best fit line can be added to show the relations

• Used to show the relationship between two variables

  • In a river study, they are used to show the relationship between different river characteristics, such as the relationship between the width and depth of the river channel

Example

Types of correlation

• Positive correlation

  • As one variable increases, so too does the other

  • The line of best fit goes from bottom left to top right of the graph

• Negative correlation 

  • As one variable increases, the other decreases

  • The line of best fit goes from the top left to the bottom right of the graph

• No correlation

  • Data points will have a scattered distribution

  • There is no relationship between the variables

Choropleth map

• These are maps that are shaded according to a pre-arranged key

• Each shade of colour represents a range of values

• It is common for one colour in different shades to be used

• Can be used for a range of data, such as annual precipitation, population density, income levels, etc.

Example

Proportional symbols map

• The symbols on the map are drawn in proportion to the variable represented

• Usually, a circle or square is used but it could be an image

• Can be used to show a range of data, for example, population, wind farms and electricity they generate, traffic or pedestrian flows

Example

Pictograms

• These are a way of displaying data using symbols or diagrams drawn to scale

• Useful way of showing data if accuracy is not too important and data is discrete

• Years do not need to be continuous

• Symbols do not need to be whole but can represent a proportion

• A key is needed to show if the total number of objects or events that image represents exceeds one

How to read a pictogram

• Step 1: Read the problem carefully and identify the specific information requested from the pictogram

• Step 2: Count the symbols corresponding to the desired information and report the count

• In the pictogram above, you can see that 4 shoppers walked to the supermarket, but only one used a taxi

• The majority of shoppers used a car to travel to the supermarket