fMonth <- factor(airquality$Month) #Convert the Month variable to a factor. 

ozone.box <- ggplot(airquality, aes(x=fMonth, y=Ozone)) + geom_boxplot()
solar.box <- ggplot(airquality, aes(x=fMonth, y=Solar.R)) + geom_boxplot()
temp.box  <- ggplot(airquality, aes(x=fMonth, y=Temp)) + geom_boxplot()
wind.box  <- ggplot(airquality, aes(x=fMonth, y=Wind)) + geom_boxplot()