连接R中绘图函数中的点的线

Question

我在R编程语言的绘图功能中有一个简单的问题.我想在点之间画一条线(参见这个链接以及如何在R中绘图),然而,我得到了一些奇怪的东西.我希望只有一个点与另一个点连接,这样我就能以连续的方式看到这个功能,但是,在我的情节点上随机连接了一些其他点.请看第二个图.

以下是代码:

x <- runif(100, -1,1) # inputs: uniformly distributed [-1,1]
noise <- rnorm(length(x), 0, 0.2) # normally distributed noise (mean=0, sd=0.2)
f_x <- 8*x^4 - 10*x^2 + x - 4  # f(x), signal without noise
y <- f_x + noise # signal with noise

# plots 
x11()
# plot of noisy data (y)
plot(x, y, xlim=range(x), ylim=range(y), xlab="x", ylab="y", 
     main = "observed noisy data", pch=16)

x11()
# plot of noiseless data (f_x)
plot(x, f_x, xlim=range(x), ylim=range(f_x), xlab="x", ylab="y", 
     main = "noise-less data",pch=16)
lines(x, f_x, xlim=range(x), ylim=range(f_x), pch=16)

# NOTE: I have also tried this (type="l" is supposed to create lines between the points in the right order), but also not working: 
plot(x, f_x, xlim=range(x), ylim=range(f_x), xlab="x", ylab="y", 
     main = "noise-less data", pch=16, type="l")

第一个图是正确的: 虽然第二个不是我想要的,但我想要一个连续的情节:

Answer 1

您必须对x值进行排序:

plot(x, f_x, xlim=range(x), ylim=range(f_x), xlab="x", ylab="y", 
     main = "noise-less data",pch=16)
lines(x[order(x)], f_x[order(x)], xlim=range(x), ylim=range(f_x), pch=16)