How to do it...

Here is how we draw simple box plot using ggplot2:

1. Begin by calling geom_boxplot() to draw box plot using ggplot2:

> library(ggplot2)
> box1 <- ggplot(data = car::Salaries, 
                 aes( x = rank, y = salary))
> box1 + geom_boxplot( outlier.alpha = .4 )

Resulting graphic looks like the following figure 3.1 (alpha blending is applied to the outliers):

Figure 3.1: Simple ggplot2 box plot

1. Similar one can be drawn by plotly:

> library(plotly)
> box2 <- plot_ly(data = car::Salaries, y = ~salary, x = ~rank, 
                  type = 'box', marker = list(opacity = .4))
> box2

1. Using ggvis, calling for alpha requires a little bit more code:

> library(ggvis)
> box3 <- ggvis(data = car::Salaries, 
                x = ~rank, y = ~salary)
> box3 %>% layer_boxplots(opacity := .4) %>% 
    layer_boxplots(size := 0)

Let's check the explanations.