如何使用ggplot2对曲线下的区域进行着色

Question

我一直在尝试使用ggplot2来生成类似于这个R图形的图：

xv<-seq(0,4,0.01)
yv<-dnorm(xv,2,0.5) 
plot(xv,yv,type="l") 
polygon(c(xv[xv<=1.5],1.5),c(yv[xv<=1.5],yv[xv==0]),col="grey") 

据我所知，ggplot2：

x<-seq(0.0,0.1699,0.0001)   
ytop<-dnorm(0.12,0.08,0.02)
MyDF<-data.frame(x=x,y=dnorm(x,0.08,0.02))
p<-qplot(x=MyDF$x,y=MyDF$y,geom="line") 
p+geom_segment(aes(x=0.12,y=0,xend=0.12,yend=ytop))

我想将尾部区域遮挡超过x = 0.12。我如何使用ggplot或qplot来做到这一点？

从广义上讲，如何对曲线下的任何子集进行着色，无论是尾部，还是在将该区域划分为不同区域的两条任意线之间？

感谢您的任何建议。

Answer 1

使用要遮蔽的区域创建多边形

#First subst the data and add the coordinates to make it shade to y = 0
shade <- rbind(c(0.12,0), subset(MyDF, x > 0.12), c(MyDF[nrow(MyDF), "X"], 0))

#Then use this new data.frame with geom_polygon
 p + geom_segment(aes(x=0.12,y=0,xend=0.12,yend=ytop)) +
     geom_polygon(data = shade, aes(x, y))

Answer 2

这实质上是我发现的有用的Luciano答案的副本，但是它可能为其他希望使用此方法的人节省时间。

创建数据。此处，密度从正态分布的0.1％到99.9％的0.001间隔，具有指定的均值和sd。

mean_ = 10
sd_ = 4

x = seq(qnorm(c(0.001), mean_, sd_),qnorm(c(0.999), mean_, sd_),0.001) 

distdata = data.frame(x=x,y=dnorm(x,mean_,sd_))

用于从特定值对左或右尾巴加阴影的功能。

shade_under_curve = function(p, d, left=NULL, right=NULL, distrib, fill, ...){

  if(!is.null(left)){

    shade = rbind(c(d[1, "x"], 0), d[d$x<left,], c(left,0))

  } else if(!is.null(right)){

    shade = rbind(c(right,0), d[d$x>right,], c(d[nrow(d), "x"], 0))

  }

  value = c(left, right)

  ytop<-distrib(value,...)

  p + geom_segment(aes(x=value,y=0,xend=value,yend=ytop)) +
    geom_polygon(data = shade, aes(x, y), alpha=0.2, fill=fill) 


}

示例：

p = qplot(x=distdata$x,y=distdata$y,geom="line") 

shade_under_curve(p, distdata, left=3, distrib=dnorm, mean=mean_, sd=sd_, fill = "red") 

shade_under_curve(p, distdata, right=15, distrib=dnorm, mean=mean_, sd=sd_, fill = "blue")

p2 = shade_under_curve(p, distdata, left=qnorm(0.025, mean_, sd_), distrib=dnorm, mean=mean_, sd=sd_, fill = "green") 
shade_under_curve(p2, distdata, right=qnorm(0.975, mean_, sd_), distrib=dnorm, mean=mean_, sd=sd_, fill = "green")