# il dataset di esempio è nel pacchetto MASS
require(MASS)

# barre verticali
plot(farms$Manag)
barplot(table(farms$Manag))

# barre orizzontali
barplot(table(farms$Manag), horiz=T, col=c(3:6), cex.axis=0.8, cex.names=0.8, 
        main="Grassland Management", names.arg=c("Biological", "Hobby", 
                                                 "Nat. Cons.", "Standard"))

# DUE VARIABILI

# costruisco la tabella
table1<-table(farms$Use,farms$Manag)

# barre raggruppate
barplot(table1, col=c(4:6),beside=T,main="Use by Management",
        legend.text=c("Hay Prod.","Intermediate","Grazing"),
        names.arg=c("Biol.", "Hobby", "Nat. Cons.", "Stand."))

# barre sovrapposte
barplot(table1, col=c(4:6),beside=F,main="Use by Management",
        legend.text=c("Hay Prod.","Intermediate","Grazing"),
        names.arg=c("Biol.", "Hobby", "Nat. Cons.", "Stand."))

# barre sovrapposte percentuali
barplot(prop.table(table1, margin=2)*100, col=c(4:6), beside=F,
        main="Use by Management",
        legend.text=c("Hay Prod.","Interm.","Grazing"),
        names.arg=c("Biol.", "Hobby", "Nat. Cons.", "Stand."))