使用segments() R循环points()

Question

我用笛卡尔坐标系中的线段将点连接起来。我坚持将点循环到线段，这样，如果我想更改点和线段的坐标，就不必每次都输入点和线段的坐标。在这里，一个for循环可能会有所帮助。

x <- -10:10
y <- -10:10

plot(x, y, type = "n", xlab = NA, ylab = NA, axes = FALSE);

axis(1, pos = 0, at = seq(-10, 10, by = 1), las=1, cex.axis=0.5)
axis(2, pos = 0, at = seq(-10, 10, by = 1), las=2, cex.axis=0.5)

points(2,1, col = "blue", pch = 20)
points(5,7, col = "blue", pch = 20)
points(-3,8, col = "green", pch = 20)
points(8,3, col = "green", pch = 20)

segments(2, 1, 5 , 7)
segments(-3, 8, 8, 3)

Answer 1

您正在重复绘制点并绘制连接这些点的线段的代码。在这些情况下，最好编写一个函数并在需要的时候调用它。

请注意，函数参数pcol代表point color，scol代表segment color。

connectPoints <- function(x, y, pcol, pch = 20, scol = "black"){
  points(x[1], x[2], col = pcol, pch = pch)
  points(y[1], y[2], col = pcol, pch = pch)
  segments(x[1], x[2], y[1], y[2], col = scol)
}

plot(x, y, type = "n", xlab = NA, ylab = NA, axes = FALSE);

axis(1, pos = 0, at = seq(-10, 10, by = 1), las=1, cex.axis=0.5)
axis(2, pos = 0, at = seq(-10, 10, by = 1), las=2, cex.axis=0.5)

x1 <- c(2, 1)
y1 <- c(5, 7)
x2 <- c(-3, 8)
y2 <- c(8, 3)

connectPoints(x1, y1, pcol = "blue")
connectPoints(x2, y2, pcol = "green")

​

​

Answer 2

使用函数分割所需的任何点：

myplot<-function(x1=sample(20),y1=sample(20),axis_range=20){
  x <- -axis_range:axis_range
  y <- -axis_range:axis_range

  plot(x, y, type = "n", xlab = NA, ylab = NA, axes = FALSE);

  axis(1, pos = 0, at = seq(-axis_range, axis_range, by = 1), las=1, cex.axis=0.5)
  axis(2, pos = 0, at = seq(-axis_range, axis_range, by = 1), las=2, cex.axis=0.5)
  cols<-sample(colors(),ceiling(length(x1)/2))
  for (i in 1:length(x1)) {
    points(x1[i],y1[i],col = cols[ceiling (i/2)], pch = 20)

  }
  for (j in 1:floor((length(x1)/2))) {
    segments(x1[(2*(j-1))+1],y1[(2*(j-1))+1],x1[2*j],y1[2*j])
  }

}
myplot(x1=sample(20),y1=sample(20),axis_range=20)

​

​