R语言正态密度曲线
x <- mtcars$mpg
h<-hist(x,
breaks=12,
col="red",
xlab="Miles Per Gallon",
main="Histogram with normal curve and box")
xfit<-seq(min(x),max(x),length=40)
yfit<-dnorm(xfit,mean=mean(x),sd=sd(x))
yfit <- yfit*diff(h$mids[1:2])*length(x)
lines(xfit, yfit, col="blue", lwd=2)
box()