在密度图中找到前10%的截断点

Question

我想要对前10%本地化的区域进行着色。我只是随意的把截断点65，来画出这个图。这就是我打算find...for每个数据集的原因。

xf <- rnorm(40000, 50, 10);
plot(density(xf),xlim=c(0,100), main = paste(names(xf), "distribution"))
dens <- density(xf)
x1 <- min(which(dens$x >= 65)) # I want identify this point such that 
# the shaded region includes top 10%

x2 <- max(which(dens$x <  max(dens$x)))
with(dens, polygon(x=c(x[c(x1,x1:x2,x2)]), y= c(0, y[x1:x2], 0), col="green"))
abline(v= mean(traitF2),  col = "black", lty = 1, lwd =2)

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Answer 1

我认为您正在寻找quantile()函数：

xf <- rnorm(40000, 50, 10)
plot(density(xf),xlim=c(0,100), main = paste(names(xf), "distribution"))
dens <- density(xf)
x1 <- min(which(dens$x >= quantile(xf, .90))) # quantile() ftw!

x2 <- max(which(dens$x <  max(dens$x)))
with(dens, polygon(x=c(x[c(x1,x1:x2,x2)]), y= c(0, y[x1:x2], 0), col="green"))

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Answer 2

您正在寻找分位数。http://en.wikipedia.org/wiki/Quantile