A good graph or chart can show as much as several paragraphs of words. But how do you choose which style of graph to use?
Types of Charts
There are several different types of charts and graphs. The four most common are probably line graphs, bar graphs and histograms, pie charts, and Cartesian graphs. They are generally used for, and best for, quite different things.
You would use:
- Bar graphs : to show numbers that are independent of each other. Example data might include things like the number of people who preferred each of Chinese takeaways, Indian takeaways and fish and chips.
- Pie charts : to show you how a whole is divided into different parts. You might, for example, want to show how a budget had been spent on different items in a particular year.
- Line graphs : show you how numbers have changed over time. They are used when you have data that are connected, and to show trends, for example, average night time temperature in each month of the year.
- Cartesian graphs : have numbers on both axes, which therefore allow you to show how changes in one thing affect another. These are widely used in mathematics, and particularly in Algebra.
- Pictograms : A pictogram is a special type of bar graph. Instead of using an axis with numbers, it uses pictures to represent a particular number of items. For example, you could use a pictogram for the data above about ages, with an image of a person to show the number of people in each category:
Axes
Graphs have two axes, the lines that run across the bottom and up the side. The line along the bottom is called the horizontal or x-axis, and the line up the side is called the vertical or y-axis.
- The x-axis may contain categories or numbers. You read it from the bottom left of the graph.
- The y-axis usually contains numbers, again starting from the bottom left of the graph.
