lines（）函数未连接图形中的实际点

Question

I have been practicing the graphs and how to plot in R with the following code

theta = 1:100
x = sin(theta)
y = cos(theta)
op = par(bg = 'white', mar = rep(1, 4))
plot.new()
plot(x,y)
plot.window(xlim = c(-1, 1), ylim = c(-1, 1))
lines(x, y, col = hsv(0.95, 1, 1))

to get the following output

Now I wanted to trace just how exactly the lines connect to form this pattern and so used the following code.

theta = 1:3
x = sin(theta)
y = cos(theta)
op = par(bg = 'white', mar = rep(1, 4))
plot(x,y, xlab = "Sin", ylab = "Cos", type = "p")
plot.window(xlim = c(-1, 1), ylim = c(-1, 1))
lines(x, y, col = hsv(0.95, 1, 1))

And I get the following output

Shouldn't the lines connect the dots? I get the output where the lines connect the dots using this code

theta = 1:3
x = sin(theta)
y = cos(theta)
op = par(bg = 'white', mar = rep(1, 4))
plot(x,y, xlab = "Sin", ylab = "Cos", type = "l")

And if I add the points later, they don't work as well.

theta = 1:3
x = sin(theta)
y = cos(theta)
op = par(bg = 'white', mar = rep(1, 4))
plot(x,y, xlab = "Sin", ylab = "Cos", type = "l")
plot.window(xlim = c(-1, 1), ylim = c(-1, 1))
points(x, y)

Here is the output.

Why is there such difference in output?

Answer 1

You are setting plot.window limits after you have plotted your points plot(...) and before plotting your lines lines(...) causing the mismatch. Try the following:

theta = 1:3
x = sin(theta)
y = cos(theta)
op = par(bg = 'white', mar = rep(1, 4))
plot.window(xlim = c(-1, 1), ylim = c(-1, 1))
plot(x,y, xlab = "Sin", ylab = "Cos", type = "p")
lines(x, y, col = hsv(0.95, 1, 1))