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Visually Representing Numerical Data | Splitting up the Whole with Pie Graphs | Showing the Overlap with Venn Diagrams | Comparing Categories with Bar Graphs | Seeking Trends with Line Graphs | Showing Orderly Data with Histograms | Functions as Graphs in the Coordinate System | Summary Visually Representing Numerical Data The modern world is complex, and includes a lot of numerical information. The modern media uses graphics to represent that complex numerical data. If we know how to interpret the graphics, then complex information can be understood more simply. However, there are many different ways to visually represent numerical data. Fortunately, these methods generally share a common structure; whatever the visual representation is, you’ll need to know how to identify which part shows "what kind" and which part shows "how much." These two qualities are the essence of visual representations of data. Please go to the link below for additional instruction for this topic included on the HSEE: Graphs of Conics: Circles & Parabolas: Splitting up the Whole with Pie Graphs When I’m showing how something has been broken up, for example, showing a budget, it is useful to use a Pie Graph. In a Pie Graph, "what kind" is represented by the different slices of the pie, and "how much" is showed by adjusting the size of the slice. For example, I could think about how I am spending my salary. If I’m spending half, or 50%, of my money on rent, 30% on my expenses (food, clothing, and so on), and 20% is savings, I would represent that data in the following pie graph.
Notice how each slice of the pie is of a size that matches the proportion – Rent is half the pie, or 50%, while Expenses are about a third, which is near 30%, and Savings is smaller than the other two. But in this simple example, we can see the weakness of using pie graphs: it is very difficult to judge exact proportions of each part, and there is no way to know what the actual values are (how much is spent on rent, for example). One way to improve the situation is to include the percentages as part of the label. You could do the same thing and have the label include the actual value, too.
If you are given data that isn’t already broken into percentages, then you should simply convert each item before attempting to write the Pie Graph. For example, the original Salary data might have been $1000 for rent, $600 for expenses, and $400 for savings. That is a total of $2000, so rent is $1000/$2000 = ½ = .50 = 50%, and similarly expenses comes out to 30% and savings to 20% as given before.
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