r - How do you draw a boxplot without specifying x axis?

Question

The base graphics can nicely plot a boxplot using a simple command

data(mtcars)
boxplot(mtcars$mpg)

But qplot requires y axis. How can I achieve with qplot the same like base graphics boxplot and not get this error?

qplot(mtcars$mpg,geom='boxplot')
Error: stat_boxplot requires the following missing aesthetics: y

Answer 1

You have to provide some dummy value to x. theme() elements are used to remove x axis title and ticks.

ggplot(mtcars,aes(x=factor(0),mpg))+geom_boxplot()+
   theme(axis.title.x=element_blank(),
    axis.text.x=element_blank(),
    axis.ticks.x=element_blank())

Or using qplot() function:

qplot(factor(0),mpg,data=mtcars,geom='boxplot')