Create Boxplot with respect to two factors using ggplot2 in R
Multiple variable distributions can be visualized with boxplots. ggplot2 allows us to create beautiful boxplots quickly. It is possible to have multiple subgroups for a variable of interest. In those situations, it is very useful to visualize using “grouped boxplots”. The ggplot2 package in R programming language provides a number of options for visualizing such grouped boxplots.
Now talking about Boxplot, then each boxplot is created for every category or level in that factor that is represented by a factor and a numerical column. geom_boxplot also allows us to plot both factors using the fill argument when there are two factors. Geom_boxplot() is the key function
Syntax:
geom_boxplot(width,notch,color,size,linetype, fill,outliner.color, outliner.size, outliner.shape)
Parameter:
- width: width of the boxplot
- notch: if it is true then it will create a notched boxplot and notches are used to compare boxplots.
- color, size,line type: borderline, color, size and shape.
- fill: used to fill box plot areas.
- outlier.colour, outlier.shape, outlier.size: The color, the shape and the size for outlying points.
Now let us look at few implementations.
Example 1:
R
# create a Data FrameGender<-sample(c("Male","Female"),20,replace=TRUE)Values<-rnorm(20,mean=0,sd=1)Group<-sample(letters[1:5],20,replace=TRUE) df<-data.frame(Gender,Values,Group) library(ggplot2) # creating a boxplotggplot(df,aes(Gender,Values))+geom_boxplot(aes(fill=Group)) |
Output:
Example 2:
R
# load ggplot2 package if already installedlibrary(ggplot2) # create a data frame with two factors df <- data.frame(Factor1=factor(rbinom(30, 1, 0.55), label=c("male","female")), Factor2=factor(rbinom(30, 1, 0.45), label=c("young","old")), Values=rnorm(30,mean=5,sd=2)) # Now make a interaction between two factors # on x axis df$Factor1Factor2 <- interaction(df$Factor1, df$Factor2) # now Plot Boxplot with fill color according# to factor1 and factor2ggplot(aes(y = Values, x = Factor1Factor2), data = df) + geom_boxplot(aes(fill=Factor1Factor2)) |
Output:
