使用矩阵更改散点图中的特定点

Question

I want to pass a matrix with x and y values that correspond to points in a scatterplot. I then want to change the color of these specific points in the scatter plot. I have looked online, but no obvious approach has stood out.

Here is the original data

set.seed(100)
rand.x <-rnorm(1000,0,1)
rand.y <-rnorm(1000,0,1)
plot(rand.x, rand.y, col='black', cex=.5, pch=20)

This is a test matrix I want to use to modify the colors of the plot from black to red.

color_changer = cbind(rand.x[1:4], rand.y[1:4])

            [,1]      [,2]
[1,] -0.50219235 1.0976501
[2,]  0.13153117 1.1810365
[3,] -0.07891709 0.5875107
[4,]  0.88678481 1.0761726

Answer 1

set.seed(100)
rand.x <-rnorm(1000,0,1)
rand.y <-rnorm(1000,0,1)
plot(rand.x, rand.y, col='black', cex=.5, pch=20)

color_changer = cbind(rand.x[1:4], rand.y[1:4])
# To add more points to the same plot use points()
points(color_changer, col='red', cex=.5, pch=20)

Answer 2

I think you could use the function lines for that, even though it is designed for lines

lines(color_changer[,1],color_changer[,2], col = "red", pch = 20, type = "p")

In this examples the type = "p" enables you to have points and the pch = 20 also dots that can stick out among the other ones.