4.1 Connecting bar charts and pie charts

Staying with the theme of food, the Eatwell Guide is part of the UK government’s healthy eating tool. The guide illustrates the different types of foods and drinks, and in the proportions in which they should be consumed, to achieve a healthy balanced diet.

Table 4 Segment sizes for the Eatwell Guide image

Figure 18 The Eatwell Guide

This healthy ‘plate’ image clearly resembles a pie chart as shown in Figure 19 below. The same information is also shown below in a bar chart (Figure 20) and a stacked bar chart (Figure21).

Figure 19 A pie chart of the Eatwell Guide

Figure 20 A bar chart of the Eatwell Guide

Figure 21 A stacked bar chart of the Eatwell Guide

Although you have not met stacked bar charts yet in this course, hopefully you can see this is formed by stacking the bars from Figure 20 one on top of the other and, in this case for ease of presentation, rotating the stacked bar horizontally.

I wonder if you have a preference to how the data is displayed above. Perhaps you find one format easier to interpret than another. Can you identify links between the graph formats?

Making the link between different formats can help consolidate for learners that for the same data set, they can have or use different representations (they draw attention to different aspects). Activity 9 demonstrates this, also helping connect angles and areas as proportions of a whole.

Activity 9

Timing: Allow 10 minutes

You will need

• A couple of sheets of paper

• Five coloured pens/pencils

• Ruler

• Scissors

• Sticky tape

Add image here

Here is the stacked bar chart for the Eatwell Guide again.

Figure 22 Stacked bar for the Eatwell Guide

Take a piece of paper, turn it landscape and draw your own copy of the bar, keeping the proportions the same (or copy this bar onto a page at the largest size it will fit and print it).Cut out the coloured bar and the tab at B as one long rectangle i.e. cut the outside dashed line around the overall bar. Wrap the bar around into a circle so the 0% end (A) is exactly touching the 100% end (B), and join the ends with sticky tape (the B serving as an overlapping tab). Place your circle on a blank piece of paper and roughly sketch around the circle on the paper.Mark the end point of each colour section on the edge of your circle and join these to the centre of the circle.Shade the segments to match the colours on your bar.

You should see something which resembles the original pie chart shown in Figure 19.