grzs

boxplot(ChickWeight[ChickWeight$Time == 21, "weight"] ~ ChickWeight[ChickWeight$Time == 21, "Diet"] ,main="Distribution du poids",ylab='poids',xlab="regime",col=c("red","blue","yellow","pink"),xaxt='n')
legend(x="topleft",legend=c("poids 1","poids 2","poids 3","poids 4"),col =c("red","blue","yellow","pink"),pch=15)
axis(1,labels=c("regime 1","regime 2","regime 3","regime 4"),at=1:4, las=2)