R语言polygon函数使用问题

Question

如图，使用polygon函数填充颜色 为什么填充到曲线外侧去了？

mean.plus.sig<-17+4*4.5
mean.minu.sig<-17-4*4.5
least.ten<-qnorm(p=0.1,mean = 17,sd=4.5)
fx.ten<-dnorm(least.ten,mean=17,sd=4.5)
nor.data<-seq(mean.minu.sig,mean.plus.sig,length=50)
fx<-dnorm(nor.data,mean = 17,sd=4.5)
plot(nor.data,fx,type="l",xlim = c(mean.minu.sig-2,mean.plus.sig+2),
     main = "Least 10% test time",xlab = "Test time x",ylab = "f(x)")
abline(h=0,col="gray")
abline(v=least.ten,lty=2)
least.data<-nor.data[nor.data<=least.ten]
least.fx<-dnorm(least.data,mean = 17,sd=4.5)
polygon(x=least.data,y=least.fx,border=NA,col="gray")

Answer 1

大概是这样，同时为了图像更精准将点数改成了500

mean.plus.sig<-17+4*4.5
mean.minu.sig<-17-4*4.5
least.ten<-qnorm(p=0.1,mean = 17,sd=4.5)
fx.ten<-dnorm(least.ten,mean=17,sd=4.5)
nor.data<-seq(mean.minu.sig,mean.plus.sig,length=500)
fx<-dnorm(nor.data,mean = 17,sd=4.5)
plot(nor.data,fx,type="l",xlim = c(mean.minu.sig-2,mean.plus.sig+2),
     main = "Least 10% test time",xlab = "Test time x",ylab = "f(x)")
abline(h=0,col="gray")
abline(v=least.ten,lty=2)

least.data<-nor.data[nor.data<=least.ten]
least.fx<-dnorm(least.data,mean = 17,sd=4.5)
polygon(x=c(least.data,least.data[length(least.data)]),y=c(least.fx,0),border=NA,col="gray")