library(MASS)
data(survey)
ng <- sum(survey$Sex=="Male",na.rm=T)
nf <- sum(survey$Sex=="Female",na.rm=T)
n <- ng+nf
dst <- density(survey$Height,na.rm=T)
dstg <- density(survey$Height[survey$Sex=="Male"],na.rm=T)
dstf <- density(survey$Height[survey$Sex=="Female"],na.rm=T)
hist(survey$Height,col="yellow",border="red",main=paste("Taille de",
nrow(survey),"étudiants"),xlab="Taille [cm]",proba=T,ylim=c(0,max(dst$y)))
lines(dstg$x,ng/n*dstg$y,lwd=3,col="darkblue")
lines(dstf$x,nf/n*dstf$y,lwd=3,lty=3,col="darkred")
lines(dst$x,dst$y)
legend(185,0.04,legend=c("Filles","Garçons"),col=c("darkred","darkblue"),
lty=c(3,1),lwd=2,pt.cex=2)