require(gplots) #for smartlegend

data(ToothGrowth)
boxplot(len ~ dose, data = ToothGrowth,
        boxwex = 0.25, at = 1:3 - 0.2,
        subset= supp == "VC", col="yellow",
        main="Guinea Pigs' Tooth Growth",
        xlab="Vitamin C dose mg",
        ylab="tooth length", ylim=c(0,35))
boxplot(len ~ dose, data = ToothGrowth, add = TRUE,
        boxwex = 0.25, at = 1:3 + 0.2,
        subset= supp == "OJ", col="orange")

smartlegend(x="left",y="top", inset = 0,
            c("Ascorbic acid", "Orange juice"),
            fill = c("yellow", "orange"))

            
            
a <- c(10,2,3,4,5,9)
b <- c(10,45,8,1,1,6)           
z <- data.frame(a,b)            
boxplot(z)