Pie Chart | Visual Display of Categorical Data

A pie chart is a way of summarizing a set of categorical data. It is a circle that is divided into segments/sectors. Each segment represents a particular category. The area of each segment is proportional to the number of cases in that category. It is a useful way of displaying the data where the division of a whole into parts needs to be presented. It can also be used to compare such divisions at different times.

Pie Chart

A pie chart is constructed by dividing the total angle of a circle of 360 degrees into different components. The angle A for each sector is obtained by the relation:

$$A=\frac{Component Part}{Total}\times 360$$

Each sector is shaded with different colors or marks so that they look separate from each other.

Example

Make an appropriate chart for the data available regarding the total production of urea fertilizer and its use on different crops. Let the total production of urea be about 200 thousand (kg) and its consumption for different crops wheat, sugarcane, maize, and lentils is 75, 80, 30, and 15 thousand (kg) respectively.

Solution:

The appropriate diagram seems to be a pie chart because we have to present a whole into 4 parts. To construct a pie chart, we calculate the proportionate arc of the circle, i.e.

CropsFertilizer (000 kg) Proportionate arc of the circle
Wheat 75  $\frac{75}{200}\times 360=135$
Sugarcane 80   $\frac{80}{200}\times 360=144$
Maize

30

$\frac{30}{200}\times 360=54$
Lentils 15   $\frac{15}{200}\times 360=27$
Total 200 360

Now draw a circle of an appropriate radius, and make the angles clockwise or anticlockwise with the help of a protractor or any other device. For wheat make an angle of 135 degrees, for sugarcane an angle of 44 degrees, for maize, an angle of 54 degrees, and for lentils, an angle of 27 degrees, hence the circular region is divided into 4 sectors. Now shade each of the sectors with different colors or marks so that they look different from each other. The pie chart of the above data is

pie chart for crop data
pie chart for crop data

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1 thought on “Pie Chart | Visual Display of Categorical Data”

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