Create Bar Chart Using ggplot2 with Ordered Facets in R

Since visualization is an essential part of data analysis, we should make sure that the plots are created in a form that is easily readable for users. For this purpose, the facets in a bar chart helps us to understand the factor variable levels for another factor. To create such type of bar chart, we can use facet_grid function of ggplot2 package.

Example

Consider the below data frame −

> set.seed(99)
> y<-sample(1:100,50,replace=TRUE)
> class<-rep(c(letters[1:5]),times=10)
> quantity<-as.factor(rep(c(5,10,15,20,25),each=10))
> df<-data.frame(y,class,quantity)

Here, we have class and quantity as factor variables. Suppose we want to use quantity as a facet.

Loading ggplot2 package −

> library(ggplot2)

Creating the plot with class on X-axis and y on Y-axis without any facet −

> ggplot(df,aes(class,y))+
+ geom_bar(stat="identity")

Output

Creating the plot with class on X-axis, y on Y-axis, and quantity as facet −

> ggplot(df,aes(class,y))+
+ geom_bar(stat="identity")+
+ facet_grid(.~quantity)

Output