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R - Pie Chart



A pie chart (or a circle chart) is a circular statistical graphic, which is divided into slices to illustrate numerical proportion. In a pie chart, the area of each slice is proportional to the quantity it represents.

The R pie() function makes a pie chart of vector x. The fractional area of each slice is given by x/sum(x). Slices are plotted counterclockwise, by default starting from the x-axis.

Syntax

pie(x, labels, radius, clockwise, main, col)

Parameters

x Required. Specify a vector of non-negative numerical quantities. The values in x are displayed as the areas of pie slices.
labels Optional. Specify one or more expressions or character strings giving names for the slices. For empty or NA (after coercion to character) labels, no label nor pointing line is drawn.
radius Optional. Specify the radius of the circle of the pie chart range from -1 to +1.
clockwise Optional. Indicates if slices are drawn clockwise or counter clockwise.
main Optional. Used to specify main title of the chart.
col Optional. Specify a vector of colors to be used in filling or shading the slices.

Example:

In the example below, a pie chart is created using data present in vector students, which represents number of students studying different languages.

#creating dataset
students <- c(50, 40, 90, 30, 60, 50)
#creating labels
langs <- c("Java", "C#", "Python", "PHP", "C++", "R")

#naming the file
png(file = "piechart.png")

#drawing the pie chart
pie(students, labels=langs)

#saving the file
dev.off()

The output of the above code will be:

Pie Chart

Example: Add features to pie chart

More features in the chart can be added using more parameters in the function, for example: to add title to the chart, main parameter is used and to add color, col parameter is used. A rainbow color pallet can be used to give different colors to each slice. The length of the pallet should be same as number of slices in the pie chart.

#creating dataset
students <- c(50, 40, 70, 30, 60, 50)
langs <- c("Java", "C#", "Python", "PHP", "C++", "R")

#naming the file
png(file = "piechart.png")

#drawing the pie chart
pie(students, labels=langs, main="Pie Chart", 
        col=rainbow(length(langs)))

#saving the file
dev.off()

The output of the above code will be:

Pie Chart

Example: Add percentages and legend to the chart

We can add percentages to each slice and legend to the chart. Consider the example below:

library(formattable)

#creating dataset
students <- c(50, 40, 70, 30, 60, 50)
slice_percentage <- percent(students/sum(students), 1)

langs <- c("Java", "C#", "Python", "PHP", "C++", "R")

#naming the file
png(file = "piechart.png")

#drawing the pie chart
pie(students, labels=slice_percentage, main="Pie Chart", 
        col=rainbow(length(langs)))

#adding legend to the pie-chart
legend("topright", langs, cex = 0.9, fill = rainbow(length(langs)))

#saving the file
dev.off()

The output of the above code will be:

Pie Chart

Example: 3D pie chart

To draw a 3D pie chart, pie3D() can be used.

library(formattable)
library(plotrix)

#creating dataset
students <- c(50, 40, 70, 30, 60, 50)
slice_percentage <- percent(students/sum(students), 1)

langs <- c("Java", "C#", "Python", "PHP", "C++", "R")

#naming the file
png(file = "piechart.png")

#drawing the pie chart
pie3D(students, labels=slice_percentage, main="Pie Chart", 
        col=rainbow(length(langs)), explode=0.1)

#adding legend to the pie-chart
legend("topright", langs, cex = 0.9, fill = rainbow(length(langs)))

#saving the file
dev.off()

The output of the above code will be:

Pie Chart

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