par(las = 2)
boxplot(pricepergallon ~ location, data = Diesel)
boxplot(pricepergallon ~ location, 
       data = droplevels(Diesel[Diesel$location == "EastCoast" | 
       Diesel$location == "Gulf" | Diesel$location == "NatAvg" | 
       Diesel$location == "Rocky" | Diesel$location == "California", ]), 
       col = "pink", main = "Exercise 2.8")
par(las = 1) 
if (FALSE) {
library(ggplot2)
ggplot2::ggplot(data = Diesel, aes(x = date, y = pricepergallon, 
           color = location)) + 
           geom_point() + 
           geom_smooth(se = FALSE) + 
           theme_bw() + 
           labs(y = "Price per Gallon (in dollars)")
}         
Run the code above in your browser using DataLab