## Graphs There are many different types of graphs.

All graphs must have certain features:

• A title
• Labelled axis indicating units used
• Even scales

### Line Graphs

Line graphs show how quantities are changing. Below are four examples: This graph shows the water heating up steadily till it boils after 6 minutes. Notice the changes in the boy's height as he moves through his teenage years. The number of containers changes considerably from month to month. Line graphs are often used to show distance and time.

### Scatter Graphs

Scatter graphs are used to show connections between two quantities.Below are two examples: There would appear to be a relationship between the mark and the time spent revising.i.e. More revision − better mark! The graphs show that if the plane is new it is cheaper and that if it is faster it is bigger.

Coordinate Graphs

Coordinate graphs are used to show a rule or relationships between x and y values. The points on the graphs below can be joined with straight lines.

Some terms to do with coordinate graphs are:
Domain The set of x-values (from the table).
Range The set of y-values (from the table).
Gradient Tells how steep a line is.
Intercept Where the lines cross the axes.

Below are two examples: This graph shows the relation x = 3. i.e. Each of the points has an x-value of 3.
This can be shown in a table:

 x 3 3 3 3 3 3 3 3 3 y 0 1 2 3 4 5 6 7 8 This graph shows the relation y = x + 2. i.e. Each of the y-values is 2 more than the x-value.
This can be shown in a table:

 x 0 1 2 3 4 5 6 y 2 3 4 5 6 7 8

### Statistical Graphs

These graphs are detailed in Topic 45.