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In the ggplot2 library for R, you can change the shape of points in a graph by adding the shape parameter to the geom_point() function. This parameter takes a numerical value ranging from 0-25 for the various shapes and sizes available. You can also use the shape parameter in other geom functions such as geom_line() and geom_jitter(). With the right combination of parameters, you can create a visually appealing graph with a range of point shapes.
You can use the shape argument to change the shape of points in a ggplot2 scatterplot:
ggplot(df, aes(x=x, y=y)) +
geom_point(shape=19)
The default value for shape is 19 (a filled-in circle), but you can specify any value between 0 to 25.
The following chart shows the shapes that correspond to each value:
library(ggplot2)
#create data frame
df <- data.frame(x=0:25, y=0:25)
#create scatter plot
ggplot(df, aes(x=x, y=y)) +
geom_point(shape=0:25, size=4)
The following examples show how to modify the shape argument in different ggplot2 scatter plots.
Example 1: Create Plot with Default Shape
The following code shows how to create a scatter plot in ggplot2 using the default shape (filled-in circle) for the points:
library(ggplot2)
#create data frame
df <- data.frame(x=0:25, y=0:25)
#create scatter plot with default point shape
ggplot(df, aes(x=x, y=y)) +
geom_point(size=4)
Since we didn’t use the shape argument to specify a point shape, ggplot2 used the default shape of a filled-in circle.
Example 2: Create Plot with Custom Shape
The following code shows how to create a scatter plot in ggplot2 using an empty triangle (shape=2) for the point shape:
library(ggplot2)
#create data frame
df <- data.frame(x=0:25, y=0:25)
#create scatter plot with custom point shape
ggplot(df, aes(x=x, y=y)) +
geom_point(shape=2, size=4)
Example 3: Create Plot with Shape Based on Value
library(ggplot2)
#create data frame
df <- data.frame(team=c('A', 'A', 'B', 'B', 'C', 'C'),
points=c(8, 11, 13, 15, 19, 25),
assists=c(4, 8, 7, 10, 11, 7))
#create scatter plot where point shape is based on team
ggplot(df, aes(x=points, y=assists, group=team)) +
geom_point(aes(shape=team, color=team), size=4)
Notice that the shape and color of the points in the plot are both based on the value for the team variable.
Notice that ggplot2 also automatically produces a legend on the right side of the plot to show which points correspond to which team.
Note: You can find the complete documentation for the geom_point() function .
The following tutorials explain how to perform other common operations in ggplot2: