Thursday, 26 December 2013

How to Make a Pie or Circle Graph

Edited by Lielie1017, MA, Maluniu, Garshepp and 1 other

Here are simple instructions on how to make a pie/circle graph.

Edit Steps

1
Use something reliable like a compass or a protractor to draw a circle. The circle and sectors must be precisely drawn!
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2
Next, add up all the numbers in the data set and make that number the denominator and each different data number the numerator for a set of fractions. Each fraction can be converted to a percentage as follows.
3
"Cross multiply" the fractions in a proportion such as if one is 3/4, then 3/4 = p/100. To get the p, use "the cross-products" 4p = 300, solving for p you get 75 or 75% (note: the p indicates the per cent). (Those cross products are the result of multiplying in a "criss-cross" pattern, called cross multiplying).
4
Multiply the numerator "p" by 3.6, to find out how many degrees the wedge would be. For 75% or p=75, multiply the number of percent by 3.6; so that 75 x 3.6 = 270 degrees (that 3.6 is based on 360 degrees split 100 ways; that is 360/100 = 3.6 and represents 1% of the circle).
- Alternatively, find 75% of 360 by multiplying .75 x 360 = 270 degrees (understand what percent means: that is 75% means "75 per 100" so that is 75/100 or is .75 in decimal form).
5
Make an angle using your protractor for the number of degrees found from the previous step, 270 degrees.
6
Label each wedge with the percentage and the category name. Instead of labeling the category name you might choose to make a key of what the different colored, numbered or lettered sectors represent in the data.
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Use a ruler to make your lines straight.
For the last wedge, which will end up without you doing anything, you should do the math and make sure it's accurate. All the sectors should add up to 100% and all the degrees summed up make 360 degrees.