如何填充R中某些特定區域的顏色？

Question

這裏的問題是：

x<-seq(0,10,length.out = 1000) 
y1<-dnorm(x,mean = 2,sd=1) 
y2<-dnorm(x,mean = 6,sd=1) 
plot(x,y1,type="l") 
lines(x,y2) 
abline(v=x[380]) 

圖表如下所示。如何在垂直線的兩側填充2種不同的顏色，例如紅色和藍色，但仍低於兩個正常密度函數。我以爲我可以使用多邊形，但失敗了。

這是無填充顏色的圖形：

Answer 1

這裏有一種方法：

首先，我們會得到你的密度的並行最低 - 這是對一個向量頂部y我們的多邊形座標。

y = pmin(y1, y2) 

# set up your plot as in the question  
plot(x, y1, type="l") 
lines(x, y2) 

# define a re-usable variable for the vertical line placement 
x_vert = 380 
abline(v = x[x_vert]) 

# Now we'll draw 2 polygons, one for the left side, one for the right. 
# The first (x,y) pairs of the polygon are just the (x,y) coords of the 
# density we're filling to, until the vertical line 
# Then we need to connect the "bottom" points, which have coordinates 
# (x[x_vert], 0) and (x[1], 0)  
polygon(x = c(x[1:x_vert], x[x_vert], x[1]), 
     y = c(y[1:x_vert], 0, 0), 
     col = "blue") 
# similar for the right hand polygon, but now going from x_vert to length(x) 
polygon(x = c(x[x_vert:length(x)], x[length(x)], x[x_vert]), 
     y = c(y[x_vert:length(x)], 0, 0), 
     col = "red") 

瞧！